21306216 has 16 divisors (see below), whose sum is σ = 53265600. Its totient is φ = 7102064.

The previous prime is 21306209. The next prime is 21306217. The reversal of 21306216 is 61260312.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21306192 and 21306201.

It is not an unprimeable number, because it can be changed into a prime (21306217) 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 3 ways as a sum of consecutive naturals, for example, 443856 + ... + 443903.

It is an arithmetic number, because the mean of its divisors is an integer number (3329100).

Almost surely, 2^21306216 is an apocalyptic number.

It is an amenable number.

21306216 is an abundant number, since it is smaller than the sum of its proper divisors (31959384).

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

21306216 is a wasteful number, since it uses less digits than its factorization.

21306216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 887768 (or 887764 counting only the distinct ones).

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

The square root of 21306216 is about 4615.8656826212. The cubic root of 21306216 is about 277.2269467338.

Adding to 21306216 its reverse (61260312), we get a palindrome (82566528).

The spelling of 21306216 in words is "twenty-one million, three hundred six thousand, two hundred sixteen".