21135664 has 80 divisors (see below), whose sum is σ = 47809440. Its totient is φ = 8960000.

The previous prime is 21135649. The next prime is 21135677. The reversal of 21135664 is 46653112.

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 209214 + ... + 209314.

It is an arithmetic number, because the mean of its divisors is an integer number (597618).

Almost surely, 2^21135664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21135664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23904720).

21135664 is an abundant number, since it is smaller than the sum of its proper divisors (26673776).

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

21135664 is a wasteful number, since it uses less digits than its factorization.

21135664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 190 (or 184 counting only the distinct ones).

The product of its digits is 4320, while the sum is 28.

The square root of 21135664 is about 4597.3540216085. The cubic root of 21135664 is about 276.4852487206.

Adding to 21135664 its reverse (46653112), we get a palindrome (67788776).

It can be divided in two parts, 2113 and 5664, that added together give a palindrome (7777).

The spelling of 21135664 in words is "twenty-one million, one hundred thirty-five thousand, six hundred sixty-four".