81659994 has 32 divisors (see below), whose sum is σ = 176964480. Its totient is φ = 24971712.

The previous prime is 81659971. The next prime is 81660001. The reversal of 81659994 is 49995618.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9892 + ... + 16160.

It is an arithmetic number, because the mean of its divisors is an integer number (5530140).

Almost surely, 2^81659994 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81659994, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (88482240).

81659994 is an abundant number, since it is smaller than the sum of its proper divisors (95304486).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81659994 is a wasteful number, since it uses less digits than its factorization.

81659994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6454.

The product of its digits is 699840, while the sum is 51.

The square root of 81659994 is about 9036.5919460823. The cubic root of 81659994 is about 433.8468493438.

The spelling of 81659994 in words is "eighty-one million, six hundred fifty-nine thousand, nine hundred ninety-four".