81521304 has 16 divisors (see below), whose sum is σ = 203803320. Its totient is φ = 27173760.

The previous prime is 81521299. The next prime is 81521309. The reversal of 81521304 is 40312518.

It is an interprime number because it is at equal distance from previous prime (81521299) and next prime (81521309).

It is a Harshad number since it is a multiple of its sum of digits (24), and also a Moran number because the ratio is a prime number: 3396721 = 81521304 / (8 + 1 + 5 + 2 + 1 + 3 + 0 + 4).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81521309) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1698337 + ... + 1698384.

Almost surely, 2^81521304 is an apocalyptic number.

It is an amenable number.

81521304 is an abundant number, since it is smaller than the sum of its proper divisors (122282016).

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

81521304 is a wasteful number, since it uses less digits than its factorization.

81521304 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3396730 (or 3396726 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 81521304 is about 9028.9148849682. The cubic root of 81521304 is about 433.6010973634.

The spelling of 81521304 in words is "eighty-one million, five hundred twenty-one thousand, three hundred four".