81775988 has 12 divisors (see below), whose sum is σ = 163552032. Its totient is φ = 35046840.

The previous prime is 81775961. The next prime is 81775997. The reversal of 81775988 is 88957718.

It is a happy number.

81775988 is an admirable number.

It is a super-2 number, since 2×81775988² = 13374624426752288, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1460258 + ... + 1460313.

It is an arithmetic number, because the mean of its divisors is an integer number (13629336).

Almost surely, 2^81775988 is an apocalyptic number.

It is an amenable number.

81775988 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

81775988 is a wasteful number, since it uses less digits than its factorization.

81775988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2920582 (or 2920580 counting only the distinct ones).

The product of its digits is 1128960, while the sum is 53.

The square root of 81775988 is about 9043.0076854993. The cubic root of 81775988 is about 434.0521715192.

The spelling of 81775988 in words is "eighty-one million, seven hundred seventy-five thousand, nine hundred eighty-eight".