81390625 has 14 divisors (see below), whose sum is σ = 101756510. Its totient is φ = 65100000.

The previous prime is 81390613. The next prime is 81390697. The reversal of 81390625 is 52609318.

It can be written as a sum of positive squares in 7 ways, for example, as 74718736 + 6671889 = 8644^2 + 2583^2 .

It is a de Polignac number, because none of the positive numbers 2^k-81390625 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 13021 + ... + 18229.

Almost surely, 2^81390625 is an apocalyptic number.

81390625 is the 5209-th octagonal number.

It is an amenable number.

81390625 is a deficient number, since it is larger than the sum of its proper divisors (20365885).

81390625 is an frugal number, since it uses more digits than its factorization.

81390625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5239 (or 5214 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 81390625 is about 9021.6752878831. The cubic root of 81390625 is about 433.3692853143.

It can be divided in two parts, 81 and 390625, that multiplied together give a 4-th power (31640625 = 75⁴).

The spelling of 81390625 in words is "eighty-one million, three hundred ninety thousand, six hundred twenty-five".