31997405261 has 4 divisors (see below), whose sum is σ = 32034483072. Its totient is φ = 31960327452.

The previous prime is 31997405257. The next prime is 31997405329. The reversal of 31997405261 is 16250479913.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16250479913 = 61211 ⋅265483.

It is a cyclic number.

It is not a de Polignac number, because 31997405261 - 2² = 31997405257 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31997405201) 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, 18537611 + ... + 18539336.

It is an arithmetic number, because the mean of its divisors is an integer number (8008620768).

Almost surely, 2^31997405261 is an apocalyptic number.

It is an amenable number.

31997405261 is a deficient number, since it is larger than the sum of its proper divisors (37077811).

31997405261 is an equidigital number, since it uses as much as digits as its factorization.

31997405261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37077810.

The product of its (nonzero) digits is 408240, while the sum is 47.

The spelling of 31997405261 in words is "thirty-one billion, nine hundred ninety-seven million, four hundred five thousand, two hundred sixty-one".