28901221 has 2 divisors, whose sum is σ = 28901222. Its totient is φ = 28901220.

The previous prime is 28901177. The next prime is 28901231. The reversal of 28901221 is 12210982.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16728100 + 12173121 = 4090^2 + 3489^2 .

It is a cyclic number.

It is not a de Polignac number, because 28901221 - 2⁹ = 28900709 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28901231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14450610 + 14450611.

It is an arithmetic number, because the mean of its divisors is an integer number (14450611).

Almost surely, 2^28901221 is an apocalyptic number.

It is an amenable number.

28901221 is a deficient number, since it is larger than the sum of its proper divisors (1).

28901221 is an equidigital number, since it uses as much as digits as its factorization.

28901221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 28901221 is about 5375.9855840581. The cubic root of 28901221 is about 306.8824577340.

The spelling of 28901221 in words is "twenty-eight million, nine hundred one thousand, two hundred twenty-one".