81523731 has 4 divisors (see below), whose sum is σ = 108698312. Its totient is φ = 54349152.

The previous prime is 81523697. The next prime is 81523751. The reversal of 81523731 is 13732518.

It is a semiprime because it is the product of two primes.

It is a de Polignac number, because none of the positive numbers 2^k-81523731 is a prime.

It is a super-2 number, since 2×81523731² = 13292237432320722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81523751) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13587286 + ... + 13587291.

It is an arithmetic number, because the mean of its divisors is an integer number (27174578).

Almost surely, 2^81523731 is an apocalyptic number.

81523731 is a deficient number, since it is larger than the sum of its proper divisors (27174581).

81523731 is a wasteful number, since it uses less digits than its factorization.

81523731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27174580.

The product of its digits is 5040, while the sum is 30.

The square root of 81523731 is about 9029.0492855007. The cubic root of 81523731 is about 433.6054002853.

The spelling of 81523731 in words is "eighty-one million, five hundred twenty-three thousand, seven hundred thirty-one".