31031401991 has 2 divisors, whose sum is σ = 31031401992. Its totient is φ = 31031401990.

The previous prime is 31031401967. The next prime is 31031402023. The reversal of 31031401991 is 19910413013.

It is an a-pointer prime, because the next prime (31031402023) can be obtained adding 31031401991 to its sum of digits (32).

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31031401991 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31031401931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15515700995 + 15515700996.

It is an arithmetic number, because the mean of its divisors is an integer number (15515700996).

Almost surely, 2^31031401991 is an apocalyptic number.

31031401991 is a deficient number, since it is larger than the sum of its proper divisors (1).

31031401991 is an equidigital number, since it uses as much as digits as its factorization.

31031401991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2916, while the sum is 32.

The spelling of 31031401991 in words is "thirty-one billion, thirty-one million, four hundred one thousand, nine hundred ninety-one".