81771992 has 32 divisors (see below), whose sum is σ = 160483680. Its totient is φ = 38987520.

The previous prime is 81771979. The next prime is 81771997. The reversal of 81771992 is 29917718.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81771997) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 95438 + ... + 96290.

It is an arithmetic number, because the mean of its divisors is an integer number (5015115).

Almost surely, 2^81771992 is an apocalyptic number.

It is an amenable number.

81771992 is a deficient number, since it is larger than the sum of its proper divisors (78711688).

81771992 is a wasteful number, since it uses less digits than its factorization.

81771992 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1403 (or 1399 counting only the distinct ones).

The product of its digits is 63504, while the sum is 44.

The square root of 81771992 is about 9042.7867386111. The cubic root of 81771992 is about 434.0451013886.

The spelling of 81771992 in words is "eighty-one million, seven hundred seventy-one thousand, nine hundred ninety-two".