31981745657 has 4 divisors (see below), whose sum is σ = 32761788276. Its totient is φ = 31201703040.

The previous prime is 31981745641. The next prime is 31981745659. The reversal of 31981745657 is 75654718913.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 14915981161 + 17065764496 = 122131^2 + 130636^2 .

It is a cyclic number.

It is not a de Polignac number, because 31981745657 - 2⁴ = 31981745641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31981745659) 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, 390021248 + ... + 390021329.

It is an arithmetic number, because the mean of its divisors is an integer number (8190447069).

Almost surely, 2^31981745657 is an apocalyptic number.

It is an amenable number.

31981745657 is a deficient number, since it is larger than the sum of its proper divisors (780042619).

31981745657 is an equidigital number, since it uses as much as digits as its factorization.

31981745657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 780042618.

The product of its digits is 6350400, while the sum is 56.

The spelling of 31981745657 in words is "thirty-one billion, nine hundred eighty-one million, seven hundred forty-five thousand, six hundred fifty-seven".