31981732561 has 2 divisors, whose sum is σ = 31981732562. Its totient is φ = 31981732560.

The previous prime is 31981732529. The next prime is 31981732637. The reversal of 31981732561 is 16523718913.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16552366336 + 15429366225 = 128656^2 + 124215^2 .

It is a cyclic number.

It is not a de Polignac number, because 31981732561 - 2⁵ = 31981732529 is a prime.

It is not a weakly prime, because it can be changed into another prime (31981739561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15990866280 + 15990866281.

It is an arithmetic number, because the mean of its divisors is an integer number (15990866281).

Almost surely, 2^31981732561 is an apocalyptic number.

It is an amenable number.

31981732561 is a deficient number, since it is larger than the sum of its proper divisors (1).

31981732561 is an equidigital number, since it uses as much as digits as its factorization.

31981732561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 272160, while the sum is 46.

The spelling of 31981732561 in words is "thirty-one billion, nine hundred eighty-one million, seven hundred thirty-two thousand, five hundred sixty-one".