81315641 has 12 divisors (see below), whose sum is σ = 94236720. Its totient is φ = 69572160.

The previous prime is 81315617. The next prime is 81315653. The reversal of 81315641 is 14651318.

It is not a de Polignac number, because 81315641 - 2²² = 77121337 is a prime.

It is a super-2 number, since 2×81315641² = 13224466942481762, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81315601) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9611 + ... + 15968.

It is an arithmetic number, because the mean of its divisors is an integer number (7853060).

Almost surely, 2^81315641 is an apocalyptic number.

It is an amenable number.

81315641 is a deficient number, since it is larger than the sum of its proper divisors (12921079).

81315641 is a wasteful number, since it uses less digits than its factorization.

81315641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25624 (or 25607 counting only the distinct ones).

The product of its digits is 2880, while the sum is 29.

The square root of 81315641 is about 9017.5185611120. The cubic root of 81315641 is about 433.2361588152.

Adding to 81315641 its reverse (14651318), we get a palindrome (95966959).

The spelling of 81315641 in words is "eighty-one million, three hundred fifteen thousand, six hundred forty-one".