21264239 has 2 divisors, whose sum is σ = 21264240. Its totient is φ = 21264238.

The previous prime is 21264223. The next prime is 21264241. The reversal of 21264239 is 93246212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21264239 - 2⁴ = 21264223 is a prime.

Together with 21264241, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21264209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10632119 + 10632120.

It is an arithmetic number, because the mean of its divisors is an integer number (10632120).

Almost surely, 2^21264239 is an apocalyptic number.

21264239 is a deficient number, since it is larger than the sum of its proper divisors (1).

21264239 is an equidigital number, since it uses as much as digits as its factorization.

21264239 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 29.

The square root of 21264239 is about 4611.3164064072. The cubic root of 21264239 is about 277.0447650591.

The spelling of 21264239 in words is "twenty-one million, two hundred sixty-four thousand, two hundred thirty-nine".