21216423 has 8 divisors (see below), whose sum is σ = 28386288. Its totient is φ = 14095424.

The previous prime is 21216413. The next prime is 21216427. The reversal of 21216423 is 32461212.

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 21216423 - 2¹⁰ = 21215399 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21216423.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216427) 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, 11190 + ... + 12947.

It is an arithmetic number, because the mean of its divisors is an integer number (3548286).

Almost surely, 2^21216423 is an apocalyptic number.

21216423 is a deficient number, since it is larger than the sum of its proper divisors (7169865).

21216423 is a wasteful number, since it uses less digits than its factorization.

21216423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24433.

The product of its digits is 576, while the sum is 21.

The square root of 21216423 is about 4606.1288518668. The cubic root of 21216423 is about 276.8369495751.

Adding to 21216423 its reverse (32461212), we get a palindrome (53677635).

The spelling of 21216423 in words is "twenty-one million, two hundred sixteen thousand, four hundred twenty-three".