21518459 has 2 divisors, whose sum is σ = 21518460. Its totient is φ = 21518458.

The previous prime is 21518411. The next prime is 21518479. The reversal of 21518459 is 95481512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21518459 - 2¹⁶ = 21452923 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21518479) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10759229 + 10759230.

It is an arithmetic number, because the mean of its divisors is an integer number (10759230).

Almost surely, 2^21518459 is an apocalyptic number.

21518459 is a deficient number, since it is larger than the sum of its proper divisors (1).

21518459 is an equidigital number, since it uses as much as digits as its factorization.

21518459 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14400, while the sum is 35.

The square root of 21518459 is about 4638.7993058549. The cubic root of 21518459 is about 278.1444438538.

The spelling of 21518459 in words is "twenty-one million, five hundred eighteen thousand, four hundred fifty-nine".