81691357544 has 16 divisors (see below), whose sum is σ = 153180222720. Its totient is φ = 40843298160.

The previous prime is 81691357487. The next prime is 81691357607. The reversal of 81691357544 is 44575319618.

It is a super-3 number, since 3×81691357544³ (a number of 34 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 147272 + ... + 430199.

It is an arithmetic number, because the mean of its divisors is an integer number (9573763920).

Almost surely, 2^81691357544 is an apocalyptic number.

It is an amenable number.

81691357544 is a deficient number, since it is larger than the sum of its proper divisors (71488865176).

81691357544 is a wasteful number, since it uses less digits than its factorization.

81691357544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 595160 (or 595156 counting only the distinct ones).

The product of its digits is 3628800, while the sum is 53.

The spelling of 81691357544 in words is "eighty-one billion, six hundred ninety-one million, three hundred fifty-seven thousand, five hundred forty-four".