21508259 has 2 divisors, whose sum is σ = 21508260. Its totient is φ = 21508258.

The previous prime is 21508241. The next prime is 21508261. The reversal of 21508259 is 95280512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21508259 - 2¹² = 21504163 is a prime.

It is a super-2 number, since 2×21508259² = 925210410422162, which contains 22 as substring.

Together with 21508261, 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 (21508229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10754129 + 10754130.

It is an arithmetic number, because the mean of its divisors is an integer number (10754130).

Almost surely, 2^21508259 is an apocalyptic number.

21508259 is a deficient number, since it is larger than the sum of its proper divisors (1).

21508259 is an equidigital number, since it uses as much as digits as its factorization.

21508259 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7200, while the sum is 32.

The square root of 21508259 is about 4637.6997531104. The cubic root of 21508259 is about 278.1004890069.

The spelling of 21508259 in words is "twenty-one million, five hundred eight thousand, two hundred fifty-nine".