81315491 has 4 divisors (see below), whose sum is σ = 81372984. Its totient is φ = 81258000.

The previous prime is 81315469. The next prime is 81315523. The reversal of 81315491 is 19451318.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81315491 is a prime.

It is a super-2 number, since 2×81315491² = 13224418153142162, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81315401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26570 + ... + 29471.

It is an arithmetic number, because the mean of its divisors is an integer number (20343246).

Almost surely, 2^81315491 is an apocalyptic number.

81315491 is a deficient number, since it is larger than the sum of its proper divisors (57493).

81315491 is a wasteful number, since it uses less digits than its factorization.

81315491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57492.

The product of its digits is 4320, while the sum is 32.

The square root of 81315491 is about 9017.5102439642. The cubic root of 81315491 is about 433.2358924234.

The spelling of 81315491 in words is "eighty-one million, three hundred fifteen thousand, four hundred ninety-one".