81321025 has 12 divisors (see below), whose sum is σ = 100950012. Its totient is φ = 64984640.

The previous prime is 81320989. The next prime is 81321043. The reversal of 81321025 is 52012318.

It can be written as a sum of positive squares in 6 ways, for example, as 913936 + 80407089 = 956^2 + 8967^2 .

It is not a de Polignac number, because 81321025 - 2¹⁵ = 81288257 is a prime.

It is a super-2 number, since 2×81321025² = 13226218214101250, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81320987 and 81321005.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 42387 + ... + 44263.

It is an arithmetic number, because the mean of its divisors is an integer number (8412501).

Almost surely, 2^81321025 is an apocalyptic number.

It is an amenable number.

81321025 is a deficient number, since it is larger than the sum of its proper divisors (19628987).

81321025 is a wasteful number, since it uses less digits than its factorization.

81321025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3620 (or 3615 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 81321025 is about 9017.8170861911. The cubic root of 81321025 is about 433.2457202886.

The spelling of 81321025 in words is "eighty-one million, three hundred twenty-one thousand, twenty-five".