81615813 has 8 divisors (see below), whose sum is σ = 110874528. Its totient is φ = 53383824.

The previous prime is 81615749. The next prime is 81615817. The reversal of 81615813 is 31851618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81615813 - 2⁶ = 81615749 is a prime.

It is a super-2 number, since 2×81615813² = 13322281863301938, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81615817) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 256495 + ... + 256812.

It is an arithmetic number, because the mean of its divisors is an integer number (13859316).

Almost surely, 2^81615813 is an apocalyptic number.

It is an amenable number.

81615813 is a deficient number, since it is larger than the sum of its proper divisors (29258715).

81615813 is a wasteful number, since it uses less digits than its factorization.

81615813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 513363.

The product of its digits is 5760, while the sum is 33.

The square root of 81615813 is about 9034.1470543710. The cubic root of 81615813 is about 433.7685929681.

It can be divided in two parts, 81615 and 813, that added together give a palindrome (82428).

The spelling of 81615813 in words is "eighty-one million, six hundred fifteen thousand, eight hundred thirteen".