28309521 has 8 divisors (see below), whose sum is σ = 37794880. Its totient is φ = 18848592.

The previous prime is 28309517. The next prime is 28309531. The reversal of 28309521 is 12590382.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 28309521 - 2² = 28309517 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28309511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3205 + ... + 8178.

It is an arithmetic number, because the mean of its divisors is an integer number (4724360).

Almost surely, 2^28309521 is an apocalyptic number.

It is an amenable number.

28309521 is a deficient number, since it is larger than the sum of its proper divisors (9485359).

28309521 is a wasteful number, since it uses less digits than its factorization.

28309521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12215.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 28309521 is about 5320.6692248250. The cubic root of 28309521 is about 304.7737137278.

The spelling of 28309521 in words is "twenty-eight million, three hundred nine thousand, five hundred twenty-one".