21345239 has 4 divisors (see below), whose sum is σ = 21556680. Its totient is φ = 21133800.

The previous prime is 21345229. The next prime is 21345241. The reversal of 21345239 is 93254312.

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 21345239 - 2⁴ = 21345223 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21345229) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105569 + ... + 105770.

It is an arithmetic number, because the mean of its divisors is an integer number (5389170).

Almost surely, 2^21345239 is an apocalyptic number.

21345239 is a deficient number, since it is larger than the sum of its proper divisors (211441).

21345239 is a wasteful number, since it uses less digits than its factorization.

21345239 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211440.

The product of its digits is 6480, while the sum is 29.

The square root of 21345239 is about 4620.0907999735. The cubic root of 21345239 is about 277.3960934469.

The spelling of 21345239 in words is "twenty-one million, three hundred forty-five thousand, two hundred thirty-nine".