81551760 has 40 divisors (see below), whose sum is σ = 252811200. Its totient is φ = 21747072.

The previous prime is 81551753. The next prime is 81551773. The reversal of 81551760 is 6715518.

It is a tau number, because it is divible by the number of its divisors (40).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 169660 + ... + 170139.

It is an arithmetic number, because the mean of its divisors is an integer number (6320280).

Almost surely, 2^81551760 is an apocalyptic number.

81551760 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81551760 is an abundant number, since it is smaller than the sum of its proper divisors (171259440).

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

81551760 is a wasteful number, since it uses less digits than its factorization.

81551760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 339815 (or 339809 counting only the distinct ones).

The product of its (nonzero) digits is 8400, while the sum is 33.

The square root of 81551760 is about 9030.6013088830. The cubic root of 81551760 is about 433.6550877936.

The spelling of 81551760 in words is "eighty-one million, five hundred fifty-one thousand, seven hundred sixty".