21030239 has 2 divisors, whose sum is σ = 21030240. Its totient is φ = 21030238.

The previous prime is 21030227. The next prime is 21030287. The reversal of 21030239 is 93203012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21030239 - 2¹² = 21026143 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21030239.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21033239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10515119 + 10515120.

It is an arithmetic number, because the mean of its divisors is an integer number (10515120).

Almost surely, 2^21030239 is an apocalyptic number.

21030239 is a deficient number, since it is larger than the sum of its proper divisors (1).

21030239 is an equidigital number, since it uses as much as digits as its factorization.

21030239 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 20.

The square root of 21030239 is about 4585.8738534766. The cubic root of 21030239 is about 276.0247781087.

The spelling of 21030239 in words is "twenty-one million, thirty thousand, two hundred thirty-nine".