81906725 has 18 divisors (see below), whose sum is σ = 104155350. Its totient is φ = 63894400.

The previous prime is 81906719. The next prime is 81906823. The reversal of 81906725 is 52760918.

It can be written as a sum of positive squares in 9 ways, for example, as 52983841 + 28922884 = 7279^2 + 5378^2 .

It is not a de Polignac number, because 81906725 - 2²⁰ = 80858149 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 41051 + ... + 42999.

Almost surely, 2^81906725 is an apocalyptic number.

It is an amenable number.

81906725 is a deficient number, since it is larger than the sum of its proper divisors (22248625).

81906725 is a wasteful number, since it uses less digits than its factorization.

81906725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2041 (or 1995 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 81906725 is about 9050.2334224041. The cubic root of 81906725 is about 434.2833578216.

The spelling of 81906725 in words is "eighty-one million, nine hundred six thousand, seven hundred twenty-five".