28904021 has 2 divisors, whose sum is σ = 28904022. Its totient is φ = 28904020.

The previous prime is 28904011. The next prime is 28904023. The reversal of 28904021 is 12040982.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 22221796 + 6682225 = 4714^2 + 2585^2 .

It is a cyclic number.

It is not a de Polignac number, because 28904021 - 2⁶ = 28903957 is a prime.

Together with 28904023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28904023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14452010 + 14452011.

It is an arithmetic number, because the mean of its divisors is an integer number (14452011).

Almost surely, 2^28904021 is an apocalyptic number.

It is an amenable number.

28904021 is a deficient number, since it is larger than the sum of its proper divisors (1).

28904021 is an equidigital number, since it uses as much as digits as its factorization.

28904021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 28904021 is about 5376.2459951159. The cubic root of 28904021 is about 306.8923678474.

The spelling of 28904021 in words is "twenty-eight million, nine hundred four thousand, twenty-one".