81072639 has 24 divisors (see below), whose sum is σ = 124492160. Its totient is φ = 50695632.

The previous prime is 81072617. The next prime is 81072647. The reversal of 81072639 is 93627018.

81072639 is a `hidden beast` number, since 8 + 10 + 7 + 2 + 639 = 666.

It is not a de Polignac number, because 81072639 - 2²¹ = 78975487 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81072239) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15312 + ... + 19914.

Almost surely, 2^81072639 is an apocalyptic number.

81072639 is a deficient number, since it is larger than the sum of its proper divisors (43419521).

81072639 is a wasteful number, since it uses less digits than its factorization.

81072639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4731 (or 4728 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 81072639 is about 9004.0345956688. The cubic root of 81072639 is about 432.8041701855.

The spelling of 81072639 in words is "eighty-one million, seventy-two thousand, six hundred thirty-nine".