81681099631 has 2 divisors, whose sum is σ = 81681099632. Its totient is φ = 81681099630.

The previous prime is 81681099623. The next prime is 81681099637. The reversal of 81681099631 is 13699018618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81681099631 - 2³ = 81681099623 is a prime.

It is a super-2 number, since 2×81681099631² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81681099637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40840549815 + 40840549816.

It is an arithmetic number, because the mean of its divisors is an integer number (40840549816).

Almost surely, 2^81681099631 is an apocalyptic number.

81681099631 is a deficient number, since it is larger than the sum of its proper divisors (1).

81681099631 is an equidigital number, since it uses as much as digits as its factorization.

81681099631 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 559872, while the sum is 52.

The spelling of 81681099631 in words is "eighty-one billion, six hundred eighty-one million, ninety-nine thousand, six hundred thirty-one".