79775981 has 2 divisors, whose sum is σ = 79775982. Its totient is φ = 79775980.

The previous prime is 79775977. The next prime is 79775999. The reversal of 79775981 is 18957797.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 40513225 + 39262756 = 6365^2 + 6266^2 .

It is a cyclic number.

It is not a de Polignac number, because 79775981 - 2² = 79775977 is a prime.

It is a super-2 number, since 2×79775981² = 12728414289024722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (79775681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39887990 + 39887991.

It is an arithmetic number, because the mean of its divisors is an integer number (39887991).

Almost surely, 2^79775981 is an apocalyptic number.

It is an amenable number.

79775981 is a deficient number, since it is larger than the sum of its proper divisors (1).

79775981 is an equidigital number, since it uses as much as digits as its factorization.

79775981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1111320, while the sum is 53.

The square root of 79775981 is about 8931.7400880232. The cubic root of 79775981 is about 430.4843667532.

The spelling of 79775981 in words is "seventy-nine million, seven hundred seventy-five thousand, nine hundred eighty-one".