21066239 has 2 divisors, whose sum is σ = 21066240. Its totient is φ = 21066238.

The previous prime is 21066233. The next prime is 21066257. The reversal of 21066239 is 93266012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21066239 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21066233) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10533119 + 10533120.

It is an arithmetic number, because the mean of its divisors is an integer number (10533120).

Almost surely, 2^21066239 is an apocalyptic number.

21066239 is a deficient number, since it is larger than the sum of its proper divisors (1).

21066239 is an equidigital number, since it uses as much as digits as its factorization.

21066239 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 29.

The square root of 21066239 is about 4589.7972722115. The cubic root of 21066239 is about 276.1821899723.

The spelling of 21066239 in words is "twenty-one million, sixty-six thousand, two hundred thirty-nine".