81638776 has 16 divisors (see below), whose sum is σ = 159728400. Its totient is φ = 39044544.

The previous prime is 81638759. The next prime is 81638803. The reversal of 81638776 is 67783618.

It is a Harshad number since it is a multiple of its sum of digits (46).

It is a congruent number.

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, 221661 + ... + 222028.

It is an arithmetic number, because the mean of its divisors is an integer number (9983025).

Almost surely, 2^81638776 is an apocalyptic number.

81638776 is the 5715-th centered pentagonal number.

It is an amenable number.

81638776 is a deficient number, since it is larger than the sum of its proper divisors (78089624).

81638776 is a wasteful number, since it uses less digits than its factorization.

81638776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 443718 (or 443714 counting only the distinct ones).

The product of its digits is 338688, while the sum is 46.

The square root of 81638776 is about 9035.4178652678. The cubic root of 81638776 is about 433.8092701107.

The spelling of 81638776 in words is "eighty-one million, six hundred thirty-eight thousand, seven hundred seventy-six".