81994140 has 48 divisors (see below), whose sum is σ = 255094560. Its totient is φ = 21864960.

The previous prime is 81994117. The next prime is 81994141. The reversal of 81994140 is 4149918.

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

It is a junction number, because it is equal to n+sod(n) for n = 81994095 and 81994104.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81994141) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 75381 + ... + 76460.

It is an arithmetic number, because the mean of its divisors is an integer number (5314470).

Almost surely, 2^81994140 is an apocalyptic number.

It is an amenable number.

81994140 is an abundant number, since it is smaller than the sum of its proper divisors (173100420).

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

81994140 is a wasteful number, since it uses less digits than its factorization.

81994140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151859 (or 151851 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The square root of 81994140 is about 9055.0615679851. The cubic root of 81994140 is about 434.4377992809.

The spelling of 81994140 in words is "eighty-one million, nine hundred ninety-four thousand, one hundred forty".