81601992 has 40 divisors (see below), whose sum is σ = 228562950. Its totient is φ = 27200448.

The previous prime is 81601991. The next prime is 81602029. The reversal of 81601992 is 29910618.

It can be written as a sum of positive squares in only one way, i.e., 51065316 + 30536676 = 7146^2 + 5526^2 .

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

It is not an unprimeable number, because it can be changed into a prime (81601991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 62317 + ... + 63612.

Almost surely, 2^81601992 is an apocalyptic number.

It is an amenable number.

81601992 is an abundant number, since it is smaller than the sum of its proper divisors (146960958).

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

81601992 is a wasteful number, since it uses less digits than its factorization.

81601992 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125947 (or 125934 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 81601992 is about 9033.3820908893. The cubic root of 81601992 is about 433.7441064790.

The spelling of 81601992 in words is "eighty-one million, six hundred one thousand, nine hundred ninety-two".