21431239 has 8 divisors (see below), whose sum is σ = 22786272. Its totient is φ = 20111520.

The previous prime is 21431231. The next prime is 21431269. The reversal of 21431239 is 93213412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21431239 - 2³ = 21431231 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 (21431231) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7572 + ... + 10009.

It is an arithmetic number, because the mean of its divisors is an integer number (2848284).

Almost surely, 2^21431239 is an apocalyptic number.

21431239 is a deficient number, since it is larger than the sum of its proper divisors (1355033).

21431239 is a wasteful number, since it uses less digits than its factorization.

21431239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17657.

The product of its digits is 1296, while the sum is 25.

The square root of 21431239 is about 4629.3886205416. The cubic root of 21431239 is about 277.7681373306.

The spelling of 21431239 in words is "twenty-one million, four hundred thirty-one thousand, two hundred thirty-nine".