81508641 has 16 divisors (see below), whose sum is σ = 113246208. Its totient is φ = 52088400.

The previous prime is 81508633. The next prime is 81508699. The reversal of 81508641 is 14680518.

It is not a de Polignac number, because 81508641 - 2³ = 81508633 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81508621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5856 + ... + 14046.

It is an arithmetic number, because the mean of its divisors is an integer number (7077888).

Almost surely, 2^81508641 is an apocalyptic number.

It is an amenable number.

81508641 is a deficient number, since it is larger than the sum of its proper divisors (31737567).

81508641 is a wasteful number, since it uses less digits than its factorization.

81508641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8332.

The product of its (nonzero) digits is 7680, while the sum is 33.

The square root of 81508641 is about 9028.2136106763. The cubic root of 81508641 is about 433.5786452568.

The spelling of 81508641 in words is "eighty-one million, five hundred eight thousand, six hundred forty-one".