81905800 has 24 divisors (see below), whose sum is σ = 190431450. Its totient is φ = 32762240.

The previous prime is 81905797. The next prime is 81905809. The reversal of 81905800 is 850918.

It can be written as a sum of positive squares in 3 ways, for example, as 42693156 + 39212644 = 6534^2 + 6262^2 .

It is not an unprimeable number, because it can be changed into a prime (81905809) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 204565 + ... + 204964.

Almost surely, 2^81905800 is an apocalyptic number.

It is an amenable number.

81905800 is an abundant number, since it is smaller than the sum of its proper divisors (108525650).

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

81905800 is a wasteful number, since it uses less digits than its factorization.

81905800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 409545 (or 409536 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 31.

The square root of 81905800 is about 9050.1823186055. The cubic root of 81905800 is about 434.2817229797.

The spelling of 81905800 in words is "eighty-one million, nine hundred five thousand, eight hundred".