81691125 has 32 divisors (see below), whose sum is σ = 136805760. Its totient is φ = 43289600.

The previous prime is 81691117. The next prime is 81691133. The reversal of 81691125 is 52119618.

It is an interprime number because it is at equal distance from previous prime (81691117) and next prime (81691133).

It is not a de Polignac number, because 81691125 - 2³ = 81691117 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 31 ways as a sum of consecutive naturals, for example, 66517 + ... + 67733.

It is an arithmetic number, because the mean of its divisors is an integer number (4275180).

Almost surely, 2^81691125 is an apocalyptic number.

It is an amenable number.

81691125 is a deficient number, since it is larger than the sum of its proper divisors (55114635).

81691125 is a wasteful number, since it uses less digits than its factorization.

81691125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1414 (or 1404 counting only the distinct ones).

The product of its digits is 4320, while the sum is 33.

The square root of 81691125 is about 9038.3142786694. The cubic root of 81691125 is about 433.9019737268.

The spelling of 81691125 in words is "eighty-one million, six hundred ninety-one thousand, one hundred twenty-five".