77691981 has 8 divisors (see below), whose sum is σ = 103750560. Its totient is φ = 51714032.

The previous prime is 77691961. The next prime is 77692009. The reversal of 77691981 is 18919677.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 77691981 - 2⁵ = 77691949 is a prime.

It is a super-2 number, since 2×77691981² = 12072087823408722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 77691981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77691961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17871 + ... + 21788.

It is an arithmetic number, because the mean of its divisors is an integer number (12968820).

Almost surely, 2^77691981 is an apocalyptic number.

It is an amenable number.

77691981 is a deficient number, since it is larger than the sum of its proper divisors (26058579).

77691981 is a wasteful number, since it uses less digits than its factorization.

77691981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40315.

The product of its digits is 190512, while the sum is 48.

The square root of 77691981 is about 8814.3054746248. The cubic root of 77691981 is about 426.7027073912.

The spelling of 77691981 in words is "seventy-seven million, six hundred ninety-one thousand, nine hundred eighty-one".