72991639 has 16 divisors (see below), whose sum is σ = 88446976. Its totient is φ = 58903200.

The previous prime is 72991619. The next prime is 72991649. The reversal of 72991639 is 93619927.

It is a cyclic number.

It is not a de Polignac number, because 72991639 - 2¹¹ = 72989591 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 (72991619) 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, 3484 + ... + 12574.

It is an arithmetic number, because the mean of its divisors is an integer number (5527936).

Almost surely, 2^72991639 is an apocalyptic number.

72991639 is a deficient number, since it is larger than the sum of its proper divisors (15455337).

72991639 is a wasteful number, since it uses less digits than its factorization.

72991639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9166.

The product of its digits is 183708, while the sum is 46.

The square root of 72991639 is about 8543.5144407907. The cubic root of 72991639 is about 417.9179631134.

The spelling of 72991639 in words is "seventy-two million, nine hundred ninety-one thousand, six hundred thirty-nine".