81997275 has 12 divisors (see below), whose sum is σ = 135568952. Its totient is φ = 43731840.

The previous prime is 81997271. The next prime is 81997309. The reversal of 81997275 is 57279918.

It is not a de Polignac number, because 81997275 - 2² = 81997271 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81997271) 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, 546574 + ... + 546723.

Almost surely, 2^81997275 is an apocalyptic number.

81997275 is a deficient number, since it is larger than the sum of its proper divisors (53571677).

81997275 is a wasteful number, since it uses less digits than its factorization.

81997275 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1093310 (or 1093305 counting only the distinct ones).

The product of its digits is 317520, while the sum is 48.

The square root of 81997275 is about 9055.2346739331. The cubic root of 81997275 is about 434.4433360390.

The spelling of 81997275 in words is "eighty-one million, nine hundred ninety-seven thousand, two hundred seventy-five".