81994120 has 128 divisors (see below), whose sum is σ = 215107200. Its totient is φ = 27869184.

The previous prime is 81994117. The next prime is 81994141. The reversal of 81994120 is 2149918.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 424744 + ... + 424936.

It is an arithmetic number, because the mean of its divisors is an integer number (1680525).

Almost surely, 2^81994120 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 81994120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (107553600).

81994120 is an abundant number, since it is smaller than the sum of its proper divisors (133113080).

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

81994120 is a wasteful number, since it uses less digits than its factorization.

81994120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279 (or 275 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 81994120 is about 9055.0604636303. The cubic root of 81994120 is about 434.4377639583.

The spelling of 81994120 in words is "eighty-one million, nine hundred ninety-four thousand, one hundred twenty".