81904551 has 16 divisors (see below), whose sum is σ = 112278144. Its totient is φ = 53079264.

The previous prime is 81904549. The next prime is 81904609. The reversal of 81904551 is 15540918.

It is not a de Polignac number, because 81904551 - 2¹ = 81904549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81904951) 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, 27885 + ... + 30681.

It is an arithmetic number, because the mean of its divisors is an integer number (7017384).

Almost surely, 2^81904551 is an apocalyptic number.

81904551 is a deficient number, since it is larger than the sum of its proper divisors (30373593).

81904551 is a wasteful number, since it uses less digits than its factorization.

81904551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3070.

The product of its (nonzero) digits is 7200, while the sum is 33.

The square root of 81904551 is about 9050.1133142077. The cubic root of 81904551 is about 434.2795154819.

The spelling of 81904551 in words is "eighty-one million, nine hundred four thousand, five hundred fifty-one".