21216736 has 24 divisors (see below), whose sum is σ = 41945904. Its totient is φ = 10563840.

The previous prime is 21216707. The next prime is 21216737. The reversal of 21216736 is 63761212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216737) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7156 + ... + 9676.

It is an arithmetic number, because the mean of its divisors is an integer number (1747746).

Almost surely, 2^21216736 is an apocalyptic number.

It is an amenable number.

21216736 is a deficient number, since it is larger than the sum of its proper divisors (20729168).

21216736 is a wasteful number, since it uses less digits than its factorization.

21216736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2794 (or 2786 counting only the distinct ones).

The product of its digits is 3024, while the sum is 28.

The square root of 21216736 is about 4606.1628282118. The cubic root of 21216736 is about 276.8383109346.

Adding to 21216736 its reverse (63761212), we get a palindrome (84977948).

It can be divided in two parts, 21216 and 736, that added together give a cube (21952 = 28³).

The spelling of 21216736 in words is "twenty-one million, two hundred sixteen thousand, seven hundred thirty-six".