81688957 has 4 divisors (see below), whose sum is σ = 93358816. Its totient is φ = 70019100.

The previous prime is 81688909. The next prime is 81689033. The reversal of 81688957 is 75988618.

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 81688957 - 2¹⁵ = 81656189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81688357) 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, 5834919 + ... + 5834932.

It is an arithmetic number, because the mean of its divisors is an integer number (23339704).

Almost surely, 2^81688957 is an apocalyptic number.

It is an amenable number.

81688957 is a deficient number, since it is larger than the sum of its proper divisors (11669859).

81688957 is a wasteful number, since it uses less digits than its factorization.

81688957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11669858.

The product of its digits is 967680, while the sum is 52.

The square root of 81688957 is about 9038.1943440048. The cubic root of 81688957 is about 433.8981352527.

The spelling of 81688957 in words is "eighty-one million, six hundred eighty-eight thousand, nine hundred fifty-seven".