81638977 has 4 divisors (see below), whose sum is σ = 93301696. Its totient is φ = 69976260.

The previous prime is 81638971. The next prime is 81638989. The reversal of 81638977 is 77983618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 77983618 = 2 ⋅38991809.

It is a cyclic number.

It is not a de Polignac number, because 81638977 - 2¹⁵ = 81606209 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81638977.

It is not an unprimeable number, because it can be changed into a prime (81638971) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5831349 + ... + 5831362.

It is an arithmetic number, because the mean of its divisors is an integer number (23325424).

Almost surely, 2^81638977 is an apocalyptic number.

It is an amenable number.

81638977 is a deficient number, since it is larger than the sum of its proper divisors (11662719).

81638977 is a wasteful number, since it uses less digits than its factorization.

81638977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11662718.

The product of its digits is 508032, while the sum is 49.

The square root of 81638977 is about 9035.4289881555. The cubic root of 81638977 is about 433.8096261327.

It can be divided in two parts, 816 and 38977, that added together give a palindrome (39793).

The spelling of 81638977 in words is "eighty-one million, six hundred thirty-eight thousand, nine hundred seventy-seven".