31978857665 has 16 divisors (see below), whose sum is σ = 38815676928. Its totient is φ = 25289673216.

The previous prime is 31978857619. The next prime is 31978857667. The reversal of 31978857665 is 56675887913.

It is a cyclic number.

It is not a de Polignac number, because 31978857665 - 2¹⁰ = 31978856641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31978857667) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 380354 + ... + 456756.

It is an arithmetic number, because the mean of its divisors is an integer number (2425979808).

Almost surely, 2^31978857665 is an apocalyptic number.

It is an amenable number.

31978857665 is a deficient number, since it is larger than the sum of its proper divisors (6836819263).

31978857665 is an equidigital number, since it uses as much as digits as its factorization.

31978857665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77368.

The product of its digits is 76204800, while the sum is 65.

The spelling of 31978857665 in words is "thirty-one billion, nine hundred seventy-eight million, eight hundred fifty-seven thousand, six hundred sixty-five".