81491715 has 24 divisors (see below), whose sum is σ = 145811328. Its totient is φ = 42059520.

The previous prime is 81491701. The next prime is 81491731. The reversal of 81491715 is 51719418.

It is not a de Polignac number, because 81491715 - 2⁶ = 81491651 is a prime.

It is a super-2 number, since 2×81491715² = 13281799227282450, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81491715.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27814 + ... + 30603.

It is an arithmetic number, because the mean of its divisors is an integer number (6075472).

Almost surely, 2^81491715 is an apocalyptic number.

81491715 is a deficient number, since it is larger than the sum of its proper divisors (64319613).

81491715 is a wasteful number, since it uses less digits than its factorization.

81491715 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58459 (or 58456 counting only the distinct ones).

The product of its digits is 10080, while the sum is 36.

The square root of 81491715 is about 9027.2761672611. The cubic root of 81491715 is about 433.5486310149.

It can be divided in two parts, 814 and 91715, that added together give a palindrome (92529).

The spelling of 81491715 in words is "eighty-one million, four hundred ninety-one thousand, seven hundred fifteen".