21216385 has 8 divisors (see below), whose sum is σ = 25588800. Its totient is φ = 16887024.

The previous prime is 21216361. The next prime is 21216389. The reversal of 21216385 is 58361212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21216385 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (21216389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9667 + ... + 11656.

It is an arithmetic number, because the mean of its divisors is an integer number (3198600).

Almost surely, 2^21216385 is an apocalyptic number.

It is an amenable number.

21216385 is a deficient number, since it is larger than the sum of its proper divisors (4372415).

21216385 is a wasteful number, since it uses less digits than its factorization.

21216385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21527.

The product of its digits is 2880, while the sum is 28.

The square root of 21216385 is about 4606.1247269261. The cubic root of 21216385 is about 276.8367842973.

Adding to 21216385 its reverse (58361212), we get a palindrome (79577597).

The spelling of 21216385 in words is "twenty-one million, two hundred sixteen thousand, three hundred eighty-five".