81947800 has 72 divisors (see below), whose sum is σ = 208931940. Its totient is φ = 29644800.

The previous prime is 81947777. The next prime is 81947813. The reversal of 81947800 is 874918.

It is a self number, because there is not a number n which added to its sum of digits gives 81947800.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 424504 + ... + 424696.

Almost surely, 2^81947800 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 81947800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (104465970).

81947800 is an abundant number, since it is smaller than the sum of its proper divisors (126984140).

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

81947800 is a wasteful number, since it uses less digits than its factorization.

81947800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 413 (or 211 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 81947800 is about 9052.5024164592. The cubic root of 81947800 is about 434.3559412303.

The spelling of 81947800 in words is "eighty-one million, nine hundred forty-seven thousand, eight hundred".