31881315391 has 2 divisors, whose sum is σ = 31881315392. Its totient is φ = 31881315390.

The previous prime is 31881315383. The next prime is 31881315397. The reversal of 31881315391 is 19351318813.

It is a strong prime.

It is an emirp because it is prime and its reverse (19351318813) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31881315391 - 2³ = 31881315383 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31881315397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15940657695 + 15940657696.

It is an arithmetic number, because the mean of its divisors is an integer number (15940657696).

Almost surely, 2^31881315391 is an apocalyptic number.

31881315391 is a deficient number, since it is larger than the sum of its proper divisors (1).

31881315391 is an equidigital number, since it uses as much as digits as its factorization.

31881315391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 77760, while the sum is 43.

The spelling of 31881315391 in words is "thirty-one billion, eight hundred eighty-one million, three hundred fifteen thousand, three hundred ninety-one".