The number 77420

Q: Is 77420 a prime number?

No. 77420 = 2^2 × 5 × 7^2 × 79, so it is divisible by 2.

77420 is a composite number with 36 divisors. Its prime factorisation is $2^{2}$ × 5 × $7^{2}$ × 79. Divisors (36): 1, 2, 4, 5, 7, 10, 14, 20, 28, 35, 49, 70, 79, 98, 140, 158 … 77420.

Number

Pick any whole number from 1 to 100,000.

77420 = 2^{2} \times 5 \times 7^{2} \times 79

Explain it step by step in chat Make a short video of it

How to work it out

1
What is special about 77420: a Harshad number: divisible by its digit sum 20.
2
77420 is composite. Its prime factorisation is
$77420 = 2^{2} \times 5 \times 7^{2} \times 79$
3
The divisors add up to 191520; without 77420 itself that is 114100, so 77420 is abundant (114100 is more than 77420). Euler's totient φ(77420) = 26208 numbers up to 77420 share no factor with it.
4
The digits of 77420 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 125 steps to reach 1.

LaTeX source of the formulas on this page

\[ 77420 = 2^{2} \times 5 \times 7^{2} \times 79 \]

77420 at a glance

Property	Value
Type	composite
Number of divisors	36
Sum of divisors	191520
Euler totient φ(n)	26208
Square	5993856400
Cube	464044362488000
Square root	278.244497 (= 14√395)
Digit sum / digital root	20 / 2
Collatz steps to 1	125
Scientific notation	7.742 × $10^{4}$

77420 in other forms

Form	Value
In words	seventy-seven thousand four hundred and twenty
Binary (base 2)	10010111001101100
Octal (base 8)	227154
Hexadecimal (base 16)	12E6C
Base 3	10221012102
As time	77420 seconds = 21 h 30 min 20 s

Is 77420 divisible by 2 to 12?

Divisor	Answer	Rule
2	Yes (77420 ÷ 2 = 38710)	A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8).
3	No (remainder 2)	A number is divisible by 3 if the digits add up to a multiple of 3.
4	Yes (77420 ÷ 4 = 19355)	A number is divisible by 4 if the last two digits make a multiple of 4.
5	Yes (77420 ÷ 5 = 15484)	A number is divisible by 5 if the last digit is 0 or 5.
6	No (remainder 2)	A number is divisible by 6 if it is divisible by both 2 and 3.
7	Yes (77420 ÷ 7 = 11060)	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 2)	A number is divisible by 9 if the digits add up to a multiple of 9.
10	Yes (77420 ÷ 10 = 7742)	A number is divisible by 10 if the last digit is 0.
11	No (remainder 2)	A number is divisible by 11 if the alternating sum of the digits is a multiple of 11.
12	No (remainder 8)	A number is divisible by 12 if it is divisible by both 3 and 4.

Questions

Is 77420 a prime number?

No. 77420 = $2^{2}$ × 5 × $7^{2}$ × 79, so it is divisible by 2.

What are the factors of 77420?

1, 2, 4, 5, 7, 10, 14, 20, 28, 35, 49, 70, 79, 98, 140, 158, 196, 245, 316, 395, 490, 553, 790, 980, 1106, 1580, 2212, 2765, 3871, 5530, 7742, 11060, 15484, 19355, 38710, 77420.

What is 77420 in binary?

10010111001101100 (hexadecimal 12E6C, octal 227154).

What is the square root of 77420?

About 278.2445, exactly 14√395.

Is 77420 divisible by 3?

No. Its digits add up to 20, which is not a multiple of 3.

What is special about the number 77420?

77420 is a Harshad number: divisible by its digit sum 20.