81037531 has 4 divisors (see below), whose sum is σ = 81401152. Its totient is φ = 80673912.

The previous prime is 81037529. The next prime is 81037543. The reversal of 81037531 is 13573018.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13573018 = 2 ⋅6786509.

It is a cyclic number.

It is not a de Polignac number, because 81037531 - 2¹ = 81037529 is a prime.

It is a super-2 number, since 2×81037531² = 13134162861151922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81037531.

It is not an unprimeable number, because it can be changed into a prime (81034531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 181476 + ... + 181921.

It is an arithmetic number, because the mean of its divisors is an integer number (20350288).

Almost surely, 2^81037531 is an apocalyptic number.

81037531 is a deficient number, since it is larger than the sum of its proper divisors (363621).

81037531 is a wasteful number, since it uses less digits than its factorization.

81037531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363620.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 81037531 is about 9002.0848140861. The cubic root of 81037531 is about 432.7416867843.

The spelling of 81037531 in words is "eighty-one million, thirty-seven thousand, five hundred thirty-one".