21216306 has 16 divisors (see below), whose sum is σ = 44928864. Its totient is φ = 6656064.

The previous prime is 21216263. The next prime is 21216361. The reversal of 21216306 is 60361212.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 103900 + ... + 104103.

It is an arithmetic number, because the mean of its divisors is an integer number (2808054).

Almost surely, 2^21216306 is an apocalyptic number.

21216306 is an abundant number, since it is smaller than the sum of its proper divisors (23712558).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21216306 is a wasteful number, since it uses less digits than its factorization.

21216306 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 208025.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21216306 is about 4606.1161513796. The cubic root of 21216306 is about 276.8364406928.

Adding to 21216306 its reverse (60361212), we get a palindrome (81577518).

The spelling of 21216306 in words is "twenty-one million, two hundred sixteen thousand, three hundred six".