77718991 has 4 divisors (see below), whose sum is σ = 88821712. Its totient is φ = 66616272.

The previous prime is 77718937. The next prime is 77718997. The reversal of 77718991 is 19981777.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 77718991 - 2¹⁹ = 77194703 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77718997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5551350 + ... + 5551363.

It is an arithmetic number, because the mean of its divisors is an integer number (22205428).

Almost surely, 2^77718991 is an apocalyptic number.

77718991 is a deficient number, since it is larger than the sum of its proper divisors (11102721).

77718991 is a wasteful number, since it uses less digits than its factorization.

77718991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11102720.

The product of its digits is 222264, while the sum is 49.

The square root of 77718991 is about 8815.8375098456. The cubic root of 77718991 is about 426.7521500949.

The spelling of 77718991 in words is "seventy-seven million, seven hundred eighteen thousand, nine hundred ninety-one".