161881756931 has 4 divisors (see below), whose sum is σ = 161882569200. Its totient is φ = 161880944664.

The previous prime is 161881756909. The next prime is 161881756943. The reversal of 161881756931 is 139657188161.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 161881756931 - 2³⁰ = 160808015107 is a prime.

It is a super-2 number, since 2×161881756931² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161881756961) 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, 120050 + ... + 581528.

It is an arithmetic number, because the mean of its divisors is an integer number (40470642300).

Almost surely, 2^161881756931 is an apocalyptic number.

161881756931 is a deficient number, since it is larger than the sum of its proper divisors (812269).

161881756931 is an equidigital number, since it uses as much as digits as its factorization.

161881756931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 812268.

The product of its digits is 2177280, while the sum is 56.

The spelling of 161881756931 in words is "one hundred sixty-one billion, eight hundred eighty-one million, seven hundred fifty-six thousand, nine hundred thirty-one".