81688071 has 4 divisors (see below), whose sum is σ = 108917432. Its totient is φ = 54458712.

The previous prime is 81687997. The next prime is 81688073. The reversal of 81688071 is 17088618.

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

It is not a de Polignac number, because 81688071 - 2²⁵ = 48133639 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 (81688073) 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, 13614676 + ... + 13614681.

It is an arithmetic number, because the mean of its divisors is an integer number (27229358).

Almost surely, 2^81688071 is an apocalyptic number.

81688071 is a deficient number, since it is larger than the sum of its proper divisors (27229361).

81688071 is a wasteful number, since it uses less digits than its factorization.

81688071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27229360.

The product of its (nonzero) digits is 21504, while the sum is 39.

The square root of 81688071 is about 9038.1453296570. The cubic root of 81688071 is about 433.8965665578.

The spelling of 81688071 in words is "eighty-one million, six hundred eighty-eight thousand, seventy-one".