21609239 has 2 divisors, whose sum is σ = 21609240. Its totient is φ = 21609238.

The previous prime is 21609233. The next prime is 21609277. The reversal of 21609239 is 93290612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21609239 - 2⁴ = 21609223 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21609233) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804619 + 10804620.

It is an arithmetic number, because the mean of its divisors is an integer number (10804620).

Almost surely, 2^21609239 is an apocalyptic number.

21609239 is a deficient number, since it is larger than the sum of its proper divisors (1).

21609239 is an equidigital number, since it uses as much as digits as its factorization.

21609239 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 32.

The square root of 21609239 is about 4648.5738673275. The cubic root of 21609239 is about 278.5350314302.

The spelling of 21609239 in words is "twenty-one million, six hundred nine thousand, two hundred thirty-nine".