28790221 has 2 divisors, whose sum is σ = 28790222. Its totient is φ = 28790220.

The previous prime is 28790219. The next prime is 28790239. The reversal of 28790221 is 12209782.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 22610025 + 6180196 = 4755^2 + 2486^2 .

It is a cyclic number.

It is not a de Polignac number, because 28790221 - 2¹ = 28790219 is a prime.

Together with 28790219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28790261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14395110 + 14395111.

It is an arithmetic number, because the mean of its divisors is an integer number (14395111).

Almost surely, 2^28790221 is an apocalyptic number.

It is an amenable number.

28790221 is a deficient number, since it is larger than the sum of its proper divisors (1).

28790221 is an equidigital number, since it uses as much as digits as its factorization.

28790221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 28790221 is about 5365.6519641140. The cubic root of 28790221 is about 306.4890757895.

The spelling of 28790221 in words is "twenty-eight million, seven hundred ninety thousand, two hundred twenty-one".