81513637 has 4 divisors (see below), whose sum is σ = 81574380. Its totient is φ = 81452896.

The previous prime is 81513613. The next prime is 81513647. The reversal of 81513637 is 73631518.

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

It can be written as a sum of positive squares in 2 ways, for example, as 44169316 + 37344321 = 6646^2 + 6111^2 .

It is a cyclic number.

It is not a de Polignac number, because 81513637 - 2²³ = 73125029 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81513647) 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, 28312 + ... + 31057.

It is an arithmetic number, because the mean of its divisors is an integer number (20393595).

Almost surely, 2^81513637 is an apocalyptic number.

It is an amenable number.

81513637 is a deficient number, since it is larger than the sum of its proper divisors (60743).

81513637 is a wasteful number, since it uses less digits than its factorization.

81513637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60742.

The product of its digits is 15120, while the sum is 34.

The square root of 81513637 is about 9028.4902946174. The cubic root of 81513637 is about 433.5875036822.

The spelling of 81513637 in words is "eighty-one million, five hundred thirteen thousand, six hundred thirty-seven".