81800560 has 20 divisors (see below), whose sum is σ = 190186488. Its totient is φ = 32720192.

The previous prime is 81800557. The next prime is 81800603. The reversal of 81800560 is 6500818.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 511174 + ... + 511333.

Almost surely, 2^81800560 is an apocalyptic number.

81800560 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81800560 is an abundant number, since it is smaller than the sum of its proper divisors (108385928).

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

81800560 is a wasteful number, since it uses less digits than its factorization.

81800560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1022520 (or 1022514 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 81800560 is about 9044.3662022278. The cubic root of 81800560 is about 434.0956417445.

The spelling of 81800560 in words is "eighty-one million, eight hundred thousand, five hundred sixty".