39928721 has 4 divisors (see below), whose sum is σ = 45632832. Its totient is φ = 34224612.

The previous prime is 39928649. The next prime is 39928739. The reversal of 39928721 is 12782993.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-39928721 is a prime.

It is not an unprimeable number, because it can be changed into a prime (39978721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2852045 + ... + 2852058.

It is an arithmetic number, because the mean of its divisors is an integer number (11408208).

Almost surely, 2^39928721 is an apocalyptic number.

It is an amenable number.

39928721 is a deficient number, since it is larger than the sum of its proper divisors (5704111).

39928721 is an equidigital number, since it uses as much as digits as its factorization.

39928721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5704110.

The product of its digits is 54432, while the sum is 41.

The square root of 39928721 is about 6318.9177079623. The cubic root of 39928721 is about 341.7919262584.

The spelling of 39928721 in words is "thirty-nine million, nine hundred twenty-eight thousand, seven hundred twenty-one".