81007992 has 128 divisors (see below), whose sum is σ = 256737600. Its totient is φ = 23445504.

The previous prime is 81007981. The next prime is 81008017. The reversal of 81007992 is 29970018.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 46888 + ... + 48584.

Almost surely, 2^81007992 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 81007992, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128368800).

81007992 is an abundant number, since it is smaller than the sum of its proper divisors (175729608).

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

81007992 is a wasteful number, since it uses less digits than its factorization.

81007992 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1742 (or 1732 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

The square root of 81007992 is about 9000.4439890485. The cubic root of 81007992 is about 432.6891008200.

The spelling of 81007992 in words is "eighty-one million, seven thousand, nine hundred ninety-two".