81685800 has 192 divisors, whose sum is σ = 321705600. Its totient is φ = 18662400.

The previous prime is 81685789. The next prime is 81685819. The reversal of 81685800 is 858618.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 36720 + ... + 38880.

It is an arithmetic number, because the mean of its divisors is an integer number (1675550).

Almost surely, 2^81685800 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81685800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (160852800).

81685800 is an abundant number, since it is smaller than the sum of its proper divisors (240019800).

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

81685800 is a wasteful number, since it uses less digits than its factorization.

81685800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2193 (or 2178 counting only the distinct ones).

The product of its (nonzero) digits is 15360, while the sum is 36.

The square root of 81685800 is about 9038.0196946012. The cubic root of 81685800 is about 433.8925456189.

The spelling of 81685800 in words is "eighty-one million, six hundred eighty-five thousand, eight hundred".