81908825 has 12 divisors (see below), whose sum is σ = 101807100. Its totient is φ = 65372160.

The previous prime is 81908809. The next prime is 81908863. The reversal of 81908825 is 52880918.

It can be written as a sum of positive squares in 6 ways, for example, as 2271049 + 79637776 = 1507^2 + 8924^2 .

It is not a de Polignac number, because 81908825 - 2⁴ = 81908809 is a prime.

It is a super-2 number, since 2×81908825² = 13418111225761250, which contains 22 as substring.

It is a Curzon number.

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 11 ways as a sum of consecutive naturals, for example, 7577 + ... + 14873.

It is an arithmetic number, because the mean of its divisors is an integer number (8483925).

Almost surely, 2^81908825 is an apocalyptic number.

It is an amenable number.

81908825 is a deficient number, since it is larger than the sum of its proper divisors (19898275).

81908825 is a wasteful number, since it uses less digits than its factorization.

81908825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7756 (or 7751 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 41.

The square root of 81908825 is about 9050.3494407675. The cubic root of 81908825 is about 434.2870693087.

The spelling of 81908825 in words is "eighty-one million, nine hundred eight thousand, eight hundred twenty-five".