81939270 has 64 divisors (see below), whose sum is σ = 229363200. Its totient is φ = 18726624.

The previous prime is 81939241. The next prime is 81939301. The reversal of 81939270 is 7293918.

It is a Curzon number.

It is a congruent number.

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, 6309 + ... + 14271.

It is an arithmetic number, because the mean of its divisors is an integer number (3583800).

Almost surely, 2^81939270 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81939270, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (114681600).

81939270 is an abundant number, since it is smaller than the sum of its proper divisors (147423930).

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

81939270 is a wasteful number, since it uses less digits than its factorization.

81939270 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7994 (or 7980 counting only the distinct ones).

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 81939270 is about 9052.0312637551. The cubic root of 81939270 is about 434.3408699095.

The spelling of 81939270 in words is "eighty-one million, nine hundred thirty-nine thousand, two hundred seventy".