81508637 has 4 divisors (see below), whose sum is σ = 93152736. Its totient is φ = 69864540.

The previous prime is 81508633. The next prime is 81508699. The reversal of 81508637 is 73680518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81508637 - 2² = 81508633 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81508637.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81508633) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5822039 + ... + 5822052.

It is an arithmetic number, because the mean of its divisors is an integer number (23288184).

Almost surely, 2^81508637 is an apocalyptic number.

It is an amenable number.

81508637 is a deficient number, since it is larger than the sum of its proper divisors (11644099).

81508637 is a wasteful number, since it uses less digits than its factorization.

81508637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11644098.

The product of its (nonzero) digits is 40320, while the sum is 38.

The square root of 81508637 is about 9028.2133891485. The cubic root of 81508637 is about 433.5786381642.

The spelling of 81508637 in words is "eighty-one million, five hundred eight thousand, six hundred thirty-seven".