28229921 has 4 divisors (see below), whose sum is σ = 28282644. Its totient is φ = 28177200.

The previous prime is 28229909. The next prime is 28229923. The reversal of 28229921 is 12992282.

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

It can be written as a sum of positive squares in 2 ways, for example, as 6477025 + 21752896 = 2545^2 + 4664^2 .

It is a cyclic number.

It is not a de Polignac number, because 28229921 - 2⁶ = 28229857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28229923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25550 + ... + 26631.

It is an arithmetic number, because the mean of its divisors is an integer number (7070661).

Almost surely, 2^28229921 is an apocalyptic number.

It is an amenable number.

28229921 is a deficient number, since it is larger than the sum of its proper divisors (52723).

28229921 is an equidigital number, since it uses as much as digits as its factorization.

28229921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52722.

The product of its digits is 10368, while the sum is 35.

The square root of 28229921 is about 5313.1836971819. The cubic root of 28229921 is about 304.4877938886.

It can be divided in two parts, 282 and 29921, that added together give a palindrome (30203).

The spelling of 28229921 in words is "twenty-eight million, two hundred twenty-nine thousand, nine hundred twenty-one".