21724064 has 24 divisors (see below), whose sum is σ = 43579620. Its totient is φ = 10656256.

The previous prime is 21724057. The next prime is 21724081. The reversal of 21724064 is 46042712.

It can be written as a sum of positive squares in 2 ways, for example, as 21715600 + 8464 = 4660^2 + 92^2 .

It is a congruent number.

It is an unprimeable number.

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, 4709 + ... + 8100.

Almost surely, 2^21724064 is an apocalyptic number.

It is an amenable number.

21724064 is an abundant number, since it is smaller than the sum of its proper divisors (21855556).

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

21724064 is a wasteful number, since it uses less digits than its factorization.

21724064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12872 (or 12864 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 26.

The square root of 21724064 is about 4660.9080660318. The cubic root of 21724064 is about 279.0275106371.

Adding to 21724064 its reverse (46042712), we get a palindrome (67766776).

The spelling of 21724064 in words is "twenty-one million, seven hundred twenty-four thousand, sixty-four".