31641981991 has 2 divisors, whose sum is σ = 31641981992. Its totient is φ = 31641981990.

The previous prime is 31641981979. The next prime is 31641982039. The reversal of 31641981991 is 19918914613.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31641981991 - 2⁹ = 31641981479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31641981191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15820990995 + 15820990996.

It is an arithmetic number, because the mean of its divisors is an integer number (15820990996).

Almost surely, 2^31641981991 is an apocalyptic number.

31641981991 is a deficient number, since it is larger than the sum of its proper divisors (1).

31641981991 is an equidigital number, since it uses as much as digits as its factorization.

31641981991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 419904, while the sum is 52.

The spelling of 31641981991 in words is "thirty-one billion, six hundred forty-one million, nine hundred eighty-one thousand, nine hundred ninety-one".