28751221 has 8 divisors (see below), whose sum is σ = 29211840. Its totient is φ = 28294368.

The previous prime is 28751207. The next prime is 28751243. The reversal of 28751221 is 12215782.

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

It is a cyclic number.

It is not a de Polignac number, because 28751221 - 2¹⁷ = 28620149 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is a self number, because there is not a number n which added to its sum of digits gives 28751221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28751201) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17065 + ... + 18673.

It is an arithmetic number, because the mean of its divisors is an integer number (3651480).

Almost surely, 2^28751221 is an apocalyptic number.

It is an amenable number.

28751221 is a deficient number, since it is larger than the sum of its proper divisors (460619).

28751221 is a wasteful number, since it uses less digits than its factorization.

28751221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1883.

The product of its digits is 2240, while the sum is 28.

The square root of 28751221 is about 5362.0165050100. The cubic root of 28751221 is about 306.3506204979.

It can be divided in two parts, 2875 and 1221, that added together give a 12-th power (4096 = 2¹²).

The spelling of 28751221 in words is "twenty-eight million, seven hundred fifty-one thousand, two hundred twenty-one".