81619904 has 28 divisors (see below), whose sum is σ = 163016184. Its totient is φ = 40545024.

The previous prime is 81619849. The next prime is 81619919. The reversal of 81619904 is 40991618.

It is a happy number.

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, 5987 + ... + 14109.

Almost surely, 2^81619904 is an apocalyptic number.

It is an amenable number.

81619904 is a deficient number, since it is larger than the sum of its proper divisors (81396280).

81619904 is a wasteful number, since it uses less digits than its factorization.

81619904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8292 (or 8282 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 38.

The square root of 81619904 is about 9034.3734702524. The cubic root of 81619904 is about 433.7758404103.

The spelling of 81619904 in words is "eighty-one million, six hundred nineteen thousand, nine hundred four".