31218617891 has 2 divisors, whose sum is σ = 31218617892. Its totient is φ = 31218617890.

The previous prime is 31218617887. The next prime is 31218617897. The reversal of 31218617891 is 19871681213.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31218617891 - 2² = 31218617887 is a prime.

It is not a weakly prime, because it can be changed into another prime (31218617897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15609308945 + 15609308946.

It is an arithmetic number, because the mean of its divisors is an integer number (15609308946).

Almost surely, 2^31218617891 is an apocalyptic number.

31218617891 is a deficient number, since it is larger than the sum of its proper divisors (1).

31218617891 is an equidigital number, since it uses as much as digits as its factorization.

31218617891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145152, while the sum is 47.

The spelling of 31218617891 in words is "thirty-one billion, two hundred eighteen million, six hundred seventeen thousand, eight hundred ninety-one".