81919984 has 20 divisors (see below), whose sum is σ = 158963040. Its totient is φ = 40897280.

The previous prime is 81919973. The next prime is 81919993. The reversal of 81919984 is 48991918.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7944 + ... + 15064.

It is an arithmetic number, because the mean of its divisors is an integer number (7948152).

Almost surely, 2^81919984 is an apocalyptic number.

It is an amenable number.

81919984 is a deficient number, since it is larger than the sum of its proper divisors (77043056).

81919984 is a wasteful number, since it uses less digits than its factorization.

81919984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7848 (or 7842 counting only the distinct ones).

The product of its digits is 186624, while the sum is 49.

The square root of 81919984 is about 9050.9659153043. The cubic root of 81919984 is about 434.3067903800.

The spelling of 81919984 in words is "eighty-one million, nine hundred nineteen thousand, nine hundred eighty-four".