21709339 has 4 divisors (see below), whose sum is σ = 21723856. Its totient is φ = 21694824.

The previous prime is 21709333. The next prime is 21709349. The reversal of 21709339 is 93390712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21709339 - 2⁵ = 21709307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21709333) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4719 + ... + 8104.

It is an arithmetic number, because the mean of its divisors is an integer number (5430964).

Almost surely, 2^21709339 is an apocalyptic number.

21709339 is a deficient number, since it is larger than the sum of its proper divisors (14517).

21709339 is a wasteful number, since it uses less digits than its factorization.

21709339 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14516.

The product of its (nonzero) digits is 10206, while the sum is 34.

The square root of 21709339 is about 4659.3281704555. The cubic root of 21709339 is about 278.9644529336.

The spelling of 21709339 in words is "twenty-one million, seven hundred nine thousand, three hundred thirty-nine".