81191525 has 12 divisors (see below), whose sum is σ = 103020192. Its totient is φ = 63441840.

The previous prime is 81191497. The next prime is 81191527. The reversal of 81191525 is 52519118.

It is a de Polignac number, because none of the positive numbers 2^k-81191525 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81191491 and 81191500.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81191527) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 36689 + ... + 38838.

It is an arithmetic number, because the mean of its divisors is an integer number (8585016).

Almost surely, 2^81191525 is an apocalyptic number.

It is an amenable number.

81191525 is a deficient number, since it is larger than the sum of its proper divisors (21828667).

81191525 is a wasteful number, since it uses less digits than its factorization.

81191525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75580 (or 75575 counting only the distinct ones).

The product of its digits is 3600, while the sum is 32.

The square root of 81191525 is about 9010.6339954523. The cubic root of 81191525 is about 433.0156234640.

The spelling of 81191525 in words is "eighty-one million, one hundred ninety-one thousand, five hundred twenty-five".