21808519 has 2 divisors, whose sum is σ = 21808520. Its totient is φ = 21808518.

The previous prime is 21808489. The next prime is 21808529. The reversal of 21808519 is 91580812.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21808519 is a prime.

It is a super-2 number, since 2×21808519² = 951223001946722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21808529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10904259 + 10904260.

It is an arithmetic number, because the mean of its divisors is an integer number (10904260).

Almost surely, 2^21808519 is an apocalyptic number.

21808519 is a deficient number, since it is larger than the sum of its proper divisors (1).

21808519 is an equidigital number, since it uses as much as digits as its factorization.

21808519 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 21808519 is about 4669.9592075306. The cubic root of 21808519 is about 279.3886277921.

The spelling of 21808519 in words is "twenty-one million, eight hundred eight thousand, five hundred nineteen".