81638625 has 32 divisors (see below), whose sum is σ = 140549760. Its totient is φ = 42033600.

The previous prime is 81638621. The next prime is 81638633. The reversal of 81638625 is 52683618.

It is a happy number.

It is not a de Polignac number, because 81638625 - 2² = 81638621 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81638621) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7122 + ... + 14628.

It is an arithmetic number, because the mean of its divisors is an integer number (4392180).

Almost surely, 2^81638625 is an apocalyptic number.

It is an amenable number.

81638625 is a deficient number, since it is larger than the sum of its proper divisors (58911135).

81638625 is a wasteful number, since it uses less digits than its factorization.

81638625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7554 (or 7544 counting only the distinct ones).

The product of its digits is 69120, while the sum is 39.

The square root of 81638625 is about 9035.4095092586. The cubic root of 81638625 is about 433.8090026511.

The spelling of 81638625 in words is "eighty-one million, six hundred thirty-eight thousand, six hundred twenty-five".