81881979 has 16 divisors (see below), whose sum is σ = 117783072. Its totient is φ = 50405888.

The previous prime is 81881977. The next prime is 81882007. The reversal of 81881979 is 97918818.

It is a cyclic number.

It is not a de Polignac number, because 81881979 - 2¹ = 81881977 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is not an unprimeable number, because it can be changed into a prime (81881977) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12444 + ... + 17849.

It is an arithmetic number, because the mean of its divisors is an integer number (7361442).

Almost surely, 2^81881979 is an apocalyptic number.

81881979 is a deficient number, since it is larger than the sum of its proper divisors (35901093).

81881979 is a wasteful number, since it uses less digits than its factorization.

81881979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30366.

The product of its digits is 290304, while the sum is 51.

The square root of 81881979 is about 9048.8661720682. The cubic root of 81881979 is about 434.2396175856.

The spelling of 81881979 in words is "eighty-one million, eight hundred eighty-one thousand, nine hundred seventy-nine".