28917521 has 2 divisors, whose sum is σ = 28917522. Its totient is φ = 28917520.

The previous prime is 28917503. The next prime is 28917523. The reversal of 28917521 is 12571982.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28890625 + 26896 = 5375^2 + 164^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28917521 is a prime.

Together with 28917523, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (28917523) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14458760 + 14458761.

It is an arithmetic number, because the mean of its divisors is an integer number (14458761).

Almost surely, 2^28917521 is an apocalyptic number.

It is an amenable number.

28917521 is a deficient number, since it is larger than the sum of its proper divisors (1).

28917521 is an equidigital number, since it uses as much as digits as its factorization.

28917521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10080, while the sum is 35.

The square root of 28917521 is about 5377.5013714550. The cubic root of 28917521 is about 306.9401397718.

The spelling of 28917521 in words is "twenty-eight million, nine hundred seventeen thousand, five hundred twenty-one".