The number 28420

Q: Is 28420 a prime number?

No. 28420 = 2^2 × 5 × 7^2 × 29, so it is divisible by 2.

28420 is a composite number with 36 divisors. Its prime factorisation is $2^{2}$ × 5 × $7^{2}$ × 29. Divisors (36): 1, 2, 4, 5, 7, 10, 14, 20, 28, 29, 35, 49, 58, 70, 98, 116 … 28420.

Number

Pick any whole number from 1 to 100,000.

28420 = 2^{2} \times 5 \times 7^{2} \times 29

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How to work it out

1
28420 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
2
28420 is composite. Its prime factorisation is
$28420 = 2^{2} \times 5 \times 7^{2} \times 29$
3
The divisors add up to 71820; without 28420 itself that is 43400, so 28420 is abundant (43400 is more than 28420). Euler's totient φ(28420) = 9408 numbers up to 28420 share no factor with it.
4
The digits of 28420 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 59 steps to reach 1.

LaTeX source of the formulas on this page

\[ 28420 = 2^{2} \times 5 \times 7^{2} \times 29 \]

28420 at a glance

Property	Value
Type	composite
Number of divisors	36
Sum of divisors	71820
Euler totient φ(n)	9408
Square	807696400
Cube	22954731688000
Square root	168.582324 (= 14√145)
Digit sum / digital root	16 / 7
Collatz steps to 1	59
Scientific notation	2.842 × $10^{4}$

28420 in other forms

Form	Value
In words	twenty-eight thousand four hundred and twenty
Binary (base 2)	110111100000100
Octal (base 8)	67404
Hexadecimal (base 16)	6F04
Base 3	1102222121
As time	28420 seconds = 7 h 53 min 40 s

Is 28420 divisible by 2 to 12?

Divisor	Answer	Rule
2	Yes (28420 ÷ 2 = 14210)	A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8).
3	No (remainder 1)	A number is divisible by 3 if the digits add up to a multiple of 3.
4	Yes (28420 ÷ 4 = 7105)	A number is divisible by 4 if the last two digits make a multiple of 4.
5	Yes (28420 ÷ 5 = 5684)	A number is divisible by 5 if the last digit is 0 or 5.
6	No (remainder 4)	A number is divisible by 6 if it is divisible by both 2 and 3.
7	Yes (28420 ÷ 7 = 4060)	A number is divisible by 7 if double the last digit and subtract it from the rest: the result is a multiple of 7.
8	No (remainder 4)	A number is divisible by 8 if the last three digits make a multiple of 8.
9	No (remainder 7)	A number is divisible by 9 if the digits add up to a multiple of 9.
10	Yes (28420 ÷ 10 = 2842)	A number is divisible by 10 if the last digit is 0.
11	No (remainder 7)	A number is divisible by 11 if the alternating sum of the digits is a multiple of 11.
12	No (remainder 4)	A number is divisible by 12 if it is divisible by both 3 and 4.

Questions

Is 28420 a prime number?

No. 28420 = $2^{2}$ × 5 × $7^{2}$ × 29, so it is divisible by 2.

What are the factors of 28420?

1, 2, 4, 5, 7, 10, 14, 20, 28, 29, 35, 49, 58, 70, 98, 116, 140, 145, 196, 203, 245, 290, 406, 490, 580, 812, 980, 1015, 1421, 2030, 2842, 4060, 5684, 7105, 14210, 28420.

What is 28420 in binary?

110111100000100 (hexadecimal 6F04, octal 67404).

What is the square root of 28420?

About 168.5823, exactly 14√145.

Is 28420 divisible by 3?

No. Its digits add up to 16, which is not a multiple of 3.

What is special about the number 28420?

It is a composite number with 36 divisors.