28724139 has 10 divisors (see below), whose sum is σ = 42909020. Its totient is φ = 19149372.

The previous prime is 28724117. The next prime is 28724147. The reversal of 28724139 is 93142782.

It is not a de Polignac number, because 28724139 - 2⁸ = 28723883 is a prime.

It is a super-2 number, since 2×28724139² = 1650152322582642, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28724159) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 177229 + ... + 177390.

It is an arithmetic number, because the mean of its divisors is an integer number (4290902).

Almost surely, 2^28724139 is an apocalyptic number.

28724139 is a deficient number, since it is larger than the sum of its proper divisors (14184881).

28724139 is an equidigital number, since it uses as much as digits as its factorization.

28724139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 354631 (or 354622 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 28724139 is about 5359.4905541478. The cubic root of 28724139 is about 306.2544020470.

The spelling of 28724139 in words is "twenty-eight million, seven hundred twenty-four thousand, one hundred thirty-nine".