81513815 has 8 divisors (see below), whose sum is σ = 97962288. Its totient is φ = 65113920.

The previous prime is 81513811. The next prime is 81513821. The reversal of 81513815 is 51831518.

It is a happy number.

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

It is not a de Polignac number, because 81513815 - 2² = 81513811 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 (81513811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8342 + ... + 15251.

It is an arithmetic number, because the mean of its divisors is an integer number (12245286).

Almost surely, 2^81513815 is an apocalyptic number.

81513815 is a deficient number, since it is larger than the sum of its proper divisors (16448473).

81513815 is a wasteful number, since it uses less digits than its factorization.

81513815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24289.

The product of its digits is 4800, while the sum is 32.

The square root of 81513815 is about 9028.5001522955. The cubic root of 81513815 is about 433.5878192880.

It can be divided in two parts, 81513 and 815, that added together give a palindrome (82328).

The spelling of 81513815 in words is "eighty-one million, five hundred thirteen thousand, eight hundred fifteen".