21216839 has 8 divisors (see below), whose sum is σ = 24278400. Its totient is φ = 18162936.

The previous prime is 21216829. The next prime is 21216841. The reversal of 21216839 is 93861212.

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 21216839 - 2¹⁶ = 21151303 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 (21216809) 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, 6512 + ... + 9210.

It is an arithmetic number, because the mean of its divisors is an integer number (3034800).

Almost surely, 2^21216839 is an apocalyptic number.

21216839 is a deficient number, since it is larger than the sum of its proper divisors (3061561).

21216839 is a wasteful number, since it uses less digits than its factorization.

21216839 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3829.

The product of its digits is 5184, while the sum is 32.

The square root of 21216839 is about 4606.1740088711. The cubic root of 21216839 is about 276.8387589190.

The spelling of 21216839 in words is "twenty-one million, two hundred sixteen thousand, eight hundred thirty-nine".