28631221 has 2 divisors, whose sum is σ = 28631222. Its totient is φ = 28631220.

The previous prime is 28631209. The next prime is 28631237. The reversal of 28631221 is 12213682.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19236996 + 9394225 = 4386^2 + 3065^2 .

It is a cyclic number.

It is not a de Polignac number, because 28631221 - 2⁵ = 28631189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28631201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14315610 + 14315611.

It is an arithmetic number, because the mean of its divisors is an integer number (14315611).

Almost surely, 2^28631221 is an apocalyptic number.

It is an amenable number.

28631221 is a deficient number, since it is larger than the sum of its proper divisors (1).

28631221 is an equidigital number, since it uses as much as digits as its factorization.

28631221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1152, while the sum is 25.

The square root of 28631221 is about 5350.8149846542. The cubic root of 28631221 is about 305.9238173087.

The spelling of 28631221 in words is "twenty-eight million, six hundred thirty-one thousand, two hundred twenty-one".