28422721 has 2 divisors, whose sum is σ = 28422722. Its totient is φ = 28422720.

The previous prime is 28422707. The next prime is 28422739. The reversal of 28422721 is 12722482.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 22848400 + 5574321 = 4780^2 + 2361^2 .

It is a cyclic number.

It is not a de Polignac number, because 28422721 - 2⁷ = 28422593 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 28422721.

It is not a weakly prime, because it can be changed into another prime (28422701) 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 as a sum of consecutive naturals, namely, 14211360 + 14211361.

It is an arithmetic number, because the mean of its divisors is an integer number (14211361).

Almost surely, 2^28422721 is an apocalyptic number.

It is an amenable number.

28422721 is a deficient number, since it is larger than the sum of its proper divisors (1).

28422721 is an equidigital number, since it uses as much as digits as its factorization.

28422721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3584, while the sum is 28.

The square root of 28422721 is about 5331.2963714279. The cubic root of 28422721 is about 305.1794017557.

It can be divided in two parts, 284 and 22721, that added together give a triangular number (23005 = T₂₁₄).

The spelling of 28422721 in words is "twenty-eight million, four hundred twenty-two thousand, seven hundred twenty-one".