21311239 has 4 divisors (see below), whose sum is σ = 21349656. Its totient is φ = 21272824.

The previous prime is 21311237. The next prime is 21311249. The reversal of 21311239 is 93211312.

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 21311239 - 2¹ = 21311237 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 (21311237) 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, 18364 + ... + 19489.

It is an arithmetic number, because the mean of its divisors is an integer number (5337414).

Almost surely, 2^21311239 is an apocalyptic number.

21311239 is a deficient number, since it is larger than the sum of its proper divisors (38417).

21311239 is an equidigital number, since it uses as much as digits as its factorization.

21311239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38416.

The product of its digits is 324, while the sum is 22.

The square root of 21311239 is about 4616.4097521776. The cubic root of 21311239 is about 277.2487306979.

The spelling of 21311239 in words is "twenty-one million, three hundred eleven thousand, two hundred thirty-nine".