81549904 has 20 divisors (see below), whose sum is σ = 164873376. Its totient is φ = 39001952.

The previous prime is 81549869. The next prime is 81549911. The reversal of 81549904 is 40994518.

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, 110434 + ... + 111169.

Almost surely, 2^81549904 is an apocalyptic number.

It is an amenable number.

81549904 is an abundant number, since it is smaller than the sum of its proper divisors (83323472).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81549904 is a wasteful number, since it uses less digits than its factorization.

81549904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221634 (or 221628 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 81549904 is about 9030.4985465920. The cubic root of 81549904 is about 433.6517979813.

The spelling of 81549904 in words is "eighty-one million, five hundred forty-nine thousand, nine hundred four".