81805800 has 48 divisors (see below), whose sum is σ = 253599840. Its totient is φ = 21814720.

The previous prime is 81805799. The next prime is 81805831. The reversal of 81805800 is 850818.

It is a super-3 number, since 3×81805800³ (a number of 25 digits) contains 333 as substring.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 67572 + ... + 68771.

It is an arithmetic number, because the mean of its divisors is an integer number (5283330).

Almost surely, 2^81805800 is an apocalyptic number.

It is an amenable number.

81805800 is an abundant number, since it is smaller than the sum of its proper divisors (171794040).

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

81805800 is a wasteful number, since it uses less digits than its factorization.

81805800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136362 (or 136353 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 30.

The square root of 81805800 is about 9044.6558806845. The cubic root of 81805800 is about 434.1049106810.

The spelling of 81805800 in words is "eighty-one million, eight hundred five thousand, eight hundred".