81540531 has 12 divisors (see below), whose sum is σ = 117875160. Its totient is φ = 54316800.

The previous prime is 81540523. The next prime is 81540559. The reversal of 81540531 is 13504518.

81540531 is a `hidden beast` number, since 81 + 54 + 0 + 531 = 666.

It is not a de Polignac number, because 81540531 - 2³ = 81540523 is a prime.

It is a super-2 number, since 2×81540531² = 13297716391523922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81540495 and 81540504.

It is not an unprimeable number, because it can be changed into a prime (81540581) 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, 11580 + ... + 17238.

It is an arithmetic number, because the mean of its divisors is an integer number (9822930).

Almost surely, 2^81540531 is an apocalyptic number.

81540531 is a deficient number, since it is larger than the sum of its proper divisors (36334629).

81540531 is a wasteful number, since it uses less digits than its factorization.

81540531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7266 (or 7263 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 27.

The square root of 81540531 is about 9029.9795680832. The cubic root of 81540531 is about 433.6351833121.

The spelling of 81540531 in words is "eighty-one million, five hundred forty thousand, five hundred thirty-one".