28701221 has 2 divisors, whose sum is σ = 28701222. Its totient is φ = 28701220.

The previous prime is 28701187. The next prime is 28701227. The reversal of 28701221 is 12210782.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20349121 + 8352100 = 4511^2 + 2890^2 .

It is a cyclic number.

It is not a de Polignac number, because 28701221 - 2⁶ = 28701157 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28701227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14350610 + 14350611.

It is an arithmetic number, because the mean of its divisors is an integer number (14350611).

Almost surely, 2^28701221 is an apocalyptic number.

It is an amenable number.

28701221 is a deficient number, since it is larger than the sum of its proper divisors (1).

28701221 is an equidigital number, since it uses as much as digits as its factorization.

28701221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 28701221 is about 5357.3520511536. The cubic root of 28701221 is about 306.1729304331.

The spelling of 28701221 in words is "twenty-eight million, seven hundred one thousand, two hundred twenty-one".