81817992 has 128 divisors (see below), whose sum is σ = 243302400. Its totient is φ = 25413696.

The previous prime is 81817963. The next prime is 81817999. The reversal of 81817992 is 29971818.

It is not an unprimeable number, because it can be changed into a prime (81817999) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 213433 + ... + 213815.

It is an arithmetic number, because the mean of its divisors is an integer number (1900800).

Almost surely, 2^81817992 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81817992, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (121651200).

81817992 is an abundant number, since it is smaller than the sum of its proper divisors (161484408).

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

81817992 is a wasteful number, since it uses less digits than its factorization.

81817992 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 464 (or 454 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 81817992 is about 9045.3298447320. The cubic root of 81817992 is about 434.1264753466.

The spelling of 81817992 in words is "eighty-one million, eight hundred seventeen thousand, nine hundred ninety-two".