21504017 has 2 divisors, whose sum is σ = 21504018. Its totient is φ = 21504016.

The previous prime is 21503981. The next prime is 21504019. The reversal of 21504017 is 71040512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18931201 + 2572816 = 4351^2 + 1604^2 .

It is a cyclic number.

It is not a de Polignac number, because 21504017 - 2¹⁰ = 21502993 is a prime.

Together with 21504019, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21504017.

It is not a weakly prime, because it can be changed into another prime (21504019) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752008 + 10752009.

It is an arithmetic number, because the mean of its divisors is an integer number (10752009).

Almost surely, 2^21504017 is an apocalyptic number.

It is an amenable number.

21504017 is a deficient number, since it is larger than the sum of its proper divisors (1).

21504017 is an equidigital number, since it uses as much as digits as its factorization.

21504017 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 21504017 is about 4637.2423917669. The cubic root of 21504017 is about 278.0822048702.

Adding to 21504017 its reverse (71040512), we get a palindrome (92544529).

The spelling of 21504017 in words is "twenty-one million, five hundred four thousand, seventeen".