21917239 has 4 divisors (see below), whose sum is σ = 22276600. Its totient is φ = 21557880.

The previous prime is 21917227. The next prime is 21917281. The reversal of 21917239 is 93271912.

It is a happy number.

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 21917239 - 2¹¹ = 21915191 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 (21917339) 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, 179589 + ... + 179710.

It is an arithmetic number, because the mean of its divisors is an integer number (5569150).

Almost surely, 2^21917239 is an apocalyptic number.

21917239 is a deficient number, since it is larger than the sum of its proper divisors (359361).

21917239 is an equidigital number, since it uses as much as digits as its factorization.

21917239 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 359360.

The product of its digits is 6804, while the sum is 34.

The square root of 21917239 is about 4681.5850948156. The cubic root of 21917239 is about 279.8521285537.

The spelling of 21917239 in words is "twenty-one million, nine hundred seventeen thousand, two hundred thirty-nine".