81221992 has 16 divisors (see below), whose sum is σ = 152409600. Its totient is φ = 40579440.

The previous prime is 81221983. The next prime is 81222007. The reversal of 81221992 is 29912218.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9817 + ... + 16087.

It is an arithmetic number, because the mean of its divisors is an integer number (9525600).

Almost surely, 2^81221992 is an apocalyptic number.

It is an amenable number.

81221992 is a deficient number, since it is larger than the sum of its proper divisors (71187608).

81221992 is a wasteful number, since it uses less digits than its factorization.

81221992 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7896 (or 7892 counting only the distinct ones).

The product of its digits is 5184, while the sum is 34.

The square root of 81221992 is about 9012.3244504401. The cubic root of 81221992 is about 433.0697795152.

The spelling of 81221992 in words is "eighty-one million, two hundred twenty-one thousand, nine hundred ninety-two".