81621568 has 112 divisors (see below), whose sum is σ = 200273920. Its totient is φ = 32223744.

The previous prime is 81621559. The next prime is 81621581. The reversal of 81621568 is 86512618.

It is a tau number, because it is divible by the number of its divisors (112).

It is a taxicab number since it can be written as a sum of two cubes in more than one way. Here 81621568 = 100³ + 432³ = 334³ + 354³.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 365905 + ... + 366127.

It is an arithmetic number, because the mean of its divisors is an integer number (1788160).

Almost surely, 2^81621568 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81621568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100136960).

81621568 is an abundant number, since it is smaller than the sum of its proper divisors (118652352).

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

81621568 is a wasteful number, since it uses less digits than its factorization.

81621568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 304 (or 294 counting only the distinct ones).

The product of its digits is 23040, while the sum is 37.

The square root of 81621568 is about 9034.4655625001. The cubic root of 81621568 is about 433.7787882129.

It can be divided in two parts, 8162 and 1568, that added together give a triangular number (9730 = T₁₃₉).

The spelling of 81621568 in words is "eighty-one million, six hundred twenty-one thousand, five hundred sixty-eight".