28917309 has 4 divisors (see below), whose sum is σ = 38556416. Its totient is φ = 19278204.

The previous prime is 28917307. The next prime is 28917337. The reversal of 28917309 is 90371982.

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 not a de Polignac number, because 28917309 - 2¹ = 28917307 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 (28917307) 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, 4819549 + ... + 4819554.

It is an arithmetic number, because the mean of its divisors is an integer number (9639104).

Almost surely, 2^28917309 is an apocalyptic number.

It is an amenable number.

28917309 is a deficient number, since it is larger than the sum of its proper divisors (9639107).

28917309 is an equidigital number, since it uses as much as digits as its factorization.

28917309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9639106.

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

The square root of 28917309 is about 5377.4816596619. The cubic root of 28917309 is about 306.9393896905.

The spelling of 28917309 in words is "twenty-eight million, nine hundred seventeen thousand, three hundred nine".