81537 has 4 divisors (see below), whose sum is σ = 108720. Its totient is φ = 54356.

The previous prime is 81533. The next prime is 81547. The reversal of 81537 is 73518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81537 - 2² = 81533 is a prime.

It is a D-number.

81537 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (81533) 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, 13587 + ... + 13592.

It is an arithmetic number, because the mean of its divisors is an integer number (27180).

2⁸¹⁵³⁷ is an apocalyptic number.

It is an amenable number.

81537 is a deficient number, since it is larger than the sum of its proper divisors (27183).

81537 is a wasteful number, since it uses less digits than its factorization.

81537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27182.

The product of its digits is 840, while the sum is 24.

The square root of 81537 is about 285.5468437927. The cubic root of 81537 is about 43.3628923898.

The spelling of 81537 in words is "eighty-one thousand, five hundred thirty-seven".