31123011991 has 2 divisors, whose sum is σ = 31123011992. Its totient is φ = 31123011990.

The previous prime is 31123011977. The next prime is 31123012031. The reversal of 31123011991 is 19911032113.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31123011991 - 2⁷ = 31123011863 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31123011191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15561505995 + 15561505996.

It is an arithmetic number, because the mean of its divisors is an integer number (15561505996).

Almost surely, 2^31123011991 is an apocalyptic number.

31123011991 is a deficient number, since it is larger than the sum of its proper divisors (1).

31123011991 is an equidigital number, since it uses as much as digits as its factorization.

31123011991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1458, while the sum is 31.

It can be divided in two parts, 3112 and 3011991, that added together give a palindrome (3015103).

The spelling of 31123011991 in words is "thirty-one billion, one hundred twenty-three million, eleven thousand, nine hundred ninety-one".