21598439 has 2 divisors, whose sum is σ = 21598440. Its totient is φ = 21598438.

The previous prime is 21598433. The next prime is 21598441. The reversal of 21598439 is 93489512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21598439 - 2⁸ = 21598183 is a prime.

Together with 21598441, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21598396 and 21598405.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21598433) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10799219 + 10799220.

It is an arithmetic number, because the mean of its divisors is an integer number (10799220).

Almost surely, 2^21598439 is an apocalyptic number.

21598439 is a deficient number, since it is larger than the sum of its proper divisors (1).

21598439 is an equidigital number, since it uses as much as digits as its factorization.

21598439 is an evil number, because the sum of its binary digits is even.

The product of its digits is 77760, while the sum is 41.

The square root of 21598439 is about 4647.4120755534. The cubic root of 21598439 is about 278.4886210402.

The spelling of 21598439 in words is "twenty-one million, five hundred ninety-eight thousand, four hundred thirty-nine".