21045239 has 2 divisors, whose sum is σ = 21045240. Its totient is φ = 21045238.

The previous prime is 21045229. The next prime is 21045257. The reversal of 21045239 is 93254012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21045239 - 2²⁰ = 19996663 is a prime.

It is equal to p_1332665 and since 21045239 and 1332665 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21045229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10522619 + 10522620.

It is an arithmetic number, because the mean of its divisors is an integer number (10522620).

Almost surely, 2^21045239 is an apocalyptic number.

21045239 is a deficient number, since it is larger than the sum of its proper divisors (1).

21045239 is an equidigital number, since it uses as much as digits as its factorization.

21045239 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 21045239 is about 4587.5090190647. The cubic root of 21045239 is about 276.0903881996.

The spelling of 21045239 in words is "twenty-one million, forty-five thousand, two hundred thirty-nine".