81800784 has 120 divisors (see below), whose sum is σ = 253416072. Its totient is φ = 24468480.

The previous prime is 81800759. The next prime is 81800791. The reversal of 81800784 is 48700818.

81800784 = 297² + 298² + ... + 647².

It can be written as a sum of positive squares in 4 ways, for example, as 31674384 + 50126400 = 5628^2 + 7080^2 .

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 68674 + ... + 69854.

Almost surely, 2^81800784 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 81800784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (126708036).

81800784 is an abundant number, since it is smaller than the sum of its proper divisors (171615288).

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

81800784 is a wasteful number, since it uses less digits than its factorization.

81800784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1245 (or 1236 counting only the distinct ones).

The product of its (nonzero) digits is 14336, while the sum is 36.

The square root of 81800784 is about 9044.3785856188. The cubic root of 81800784 is about 434.0960379820.

The spelling of 81800784 in words is "eighty-one million, eight hundred thousand, seven hundred eighty-four".