28591921 has 6 divisors (see below), whose sum is σ = 29889650. Its totient is φ = 27348288.

The previous prime is 28591919. The next prime is 28591939. The reversal of 28591921 is 12919582.

It can be written as a sum of positive squares in only one way, i.e., 28472896 + 119025 = 5336^2 + 345^2 .

It is not a de Polignac number, because 28591921 - 2¹ = 28591919 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28591961) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 26496 + ... + 27553.

Almost surely, 2^28591921 is an apocalyptic number.

It is an amenable number.

28591921 is a deficient number, since it is larger than the sum of its proper divisors (1297729).

28591921 is an equidigital number, since it uses as much as digits as its factorization.

28591921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54095 (or 54072 counting only the distinct ones).

The product of its digits is 12960, while the sum is 37.

The square root of 28591921 is about 5347.1413858248. The cubic root of 28591921 is about 305.7837800726.

The spelling of 28591921 in words is "twenty-eight million, five hundred ninety-one thousand, nine hundred twenty-one".