21506339 has 2 divisors, whose sum is σ = 21506340. Its totient is φ = 21506338.

The previous prime is 21506333. The next prime is 21506341. The reversal of 21506339 is 93360512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21506339 - 2⁴ = 21506323 is a prime.

Together with 21506341, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21506333) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753169 + 10753170.

It is an arithmetic number, because the mean of its divisors is an integer number (10753170).

Almost surely, 2^21506339 is an apocalyptic number.

21506339 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506339 is an equidigital number, since it uses as much as digits as its factorization.

21506339 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4860, while the sum is 29.

The square root of 21506339 is about 4637.4927493205. The cubic root of 21506339 is about 278.0922135993.

The spelling of 21506339 in words is "twenty-one million, five hundred six thousand, three hundred thirty-nine".