81617777768 has 32 divisors (see below), whose sum is σ = 154786658400. Its totient is φ = 40343030208.

The previous prime is 81617777753. The next prime is 81617777789. The reversal of 81617777768 is 86777771618.

It is a super-2 number, since 2×81617777768² (a number of 23 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 280655 + ... + 491937.

It is an arithmetic number, because the mean of its divisors is an integer number (4837083075).

Almost surely, 2^81617777768 is an apocalyptic number.

It is an amenable number.

81617777768 is a deficient number, since it is larger than the sum of its proper divisors (73168880632).

81617777768 is a wasteful number, since it uses less digits than its factorization.

81617777768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 211841 (or 211837 counting only the distinct ones).

The product of its digits is 38723328, while the sum is 65.

The spelling of 81617777768 in words is "eighty-one billion, six hundred seventeen million, seven hundred seventy-seven thousand, seven hundred sixty-eight".