28221569 has 4 divisors (see below), whose sum is σ = 28232196. Its totient is φ = 28210944.

The previous prime is 28221551. The next prime is 28221601. The reversal of 28221569 is 96512282.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 96512282 = 2 ⋅48256141.

It can be written as a sum of positive squares in 2 ways, for example, as 27040000 + 1181569 = 5200^2 + 1087^2 .

It is a cyclic number.

It is not a de Polignac number, because 28221569 - 2⁸ = 28221313 is a prime.

It is a super-2 number, since 2×28221569² = 1592913913643522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28221509) 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, 2537 + ... + 7929.

It is an arithmetic number, because the mean of its divisors is an integer number (7058049).

Almost surely, 2^28221569 is an apocalyptic number.

It is an amenable number.

28221569 is a deficient number, since it is larger than the sum of its proper divisors (10627).

28221569 is an equidigital number, since it uses as much as digits as its factorization.

28221569 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10626.

The product of its digits is 17280, while the sum is 35.

The square root of 28221569 is about 5312.3976696027. The cubic root of 28221569 is about 304.4577627160.

The spelling of 28221569 in words is "twenty-eight million, two hundred twenty-one thousand, five hundred sixty-nine".