21216735 has 20 divisors (see below), whose sum is σ = 38033688. Its totient is φ = 11315376.

The previous prime is 21216707. The next prime is 21216737. The reversal of 21216735 is 53761212.

It is a happy number.

It is not a de Polignac number, because 21216735 - 2⁷ = 21216607 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21216699 and 21216708.

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 (17) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 25789 + ... + 26598.

Almost surely, 2^21216735 is an apocalyptic number.

21216735 is a deficient number, since it is larger than the sum of its proper divisors (16816953).

21216735 is an equidigital number, since it uses as much as digits as its factorization.

21216735 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52404 (or 52395 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21216735 is about 4606.1627196616. The cubic root of 21216735 is about 276.8383065852.

Adding to 21216735 its reverse (53761212), we get a palindrome (74977947).

The spelling of 21216735 in words is "twenty-one million, two hundred sixteen thousand, seven hundred thirty-five".