81531275 has 12 divisors (see below), whose sum is σ = 115541712. Its totient is φ = 55907040.

The previous prime is 81531259. The next prime is 81531277. The reversal of 81531275 is 57213518.

It is not a de Polignac number, because 81531275 - 2⁴ = 81531259 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81531277) 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, 232772 + ... + 233121.

It is an arithmetic number, because the mean of its divisors is an integer number (9628476).

Almost surely, 2^81531275 is an apocalyptic number.

81531275 is a deficient number, since it is larger than the sum of its proper divisors (34010437).

81531275 is a wasteful number, since it uses less digits than its factorization.

81531275 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 465910 (or 465905 counting only the distinct ones).

The product of its digits is 8400, while the sum is 32.

The square root of 81531275 is about 9029.4670385356. The cubic root of 81531275 is about 433.6187747887.

The spelling of 81531275 in words is "eighty-one million, five hundred thirty-one thousand, two hundred seventy-five".