28125221 has 8 divisors (see below), whose sum is σ = 29208984. Its totient is φ = 27060480.

The previous prime is 28125203. The next prime is 28125233. The reversal of 28125221 is 12252182.

It can be written as a sum of positive squares in 4 ways, for example, as 1240996 + 26884225 = 1114^2 + 5185^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28125221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28125421) 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 7 ways as a sum of consecutive naturals, for example, 1706 + ... + 7691.

It is an arithmetic number, because the mean of its divisors is an integer number (3651123).

Almost surely, 2^28125221 is an apocalyptic number.

It is an amenable number.

28125221 is a deficient number, since it is larger than the sum of its proper divisors (1083763).

28125221 is an equidigital number, since it uses as much as digits as its factorization.

28125221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9511.

The product of its digits is 640, while the sum is 23.

The square root of 28125221 is about 5303.3216949380. The cubic root of 28125221 is about 304.1108963198.

The spelling of 28125221 in words is "twenty-eight million, one hundred twenty-five thousand, two hundred twenty-one".