28221331 has 4 divisors (see below), whose sum is σ = 28394632. Its totient is φ = 28048032.

The previous prime is 28221329. The next prime is 28221337. The reversal of 28221331 is 13312282.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 28221331 - 2¹ = 28221329 is a prime.

It is a super-2 number, since 2×28221331² = 1592887046823122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28221337) 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, 86406 + ... + 86731.

It is an arithmetic number, because the mean of its divisors is an integer number (7098658).

Almost surely, 2^28221331 is an apocalyptic number.

28221331 is a deficient number, since it is larger than the sum of its proper divisors (173301).

28221331 is a wasteful number, since it uses less digits than its factorization.

28221331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173300.

The product of its digits is 576, while the sum is 22.

The square root of 28221331 is about 5312.3752691240. The cubic root of 28221331 is about 304.4569068558.

The spelling of 28221331 in words is "twenty-eight million, two hundred twenty-one thousand, three hundred thirty-one".