81368661618631 has 2 divisors, whose sum is σ = 81368661618632. Its totient is φ = 81368661618630.

The previous prime is 81368661618571. The next prime is 81368661618679. The reversal of 81368661618631 is 13681616686318.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81368661618631 - 2¹⁷ = 81368661487559 is a prime.

It is a super-2 number, since 2×81368661618631² (a number of 29 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81368661618131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40684330809315 + 40684330809316.

It is an arithmetic number, because the mean of its divisors is an integer number (40684330809316).

Almost surely, 2^{81368661618631} is an apocalyptic number.

81368661618631 is a deficient number, since it is larger than the sum of its proper divisors (1).

81368661618631 is an equidigital number, since it uses as much as digits as its factorization.

81368661618631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 35831808, while the sum is 64.

The spelling of 81368661618631 in words is "eighty-one trillion, three hundred sixty-eight billion, six hundred sixty-one million, six hundred eighteen thousand, six hundred thirty-one".