21006568 has 24 divisors (see below), whose sum is σ = 43295490. Its totient is φ = 9548000.

The previous prime is 21006563. The next prime is 21006593. The reversal of 21006568 is 86560012.

It can be written as a sum of positive squares in only one way, i.e., 14152644 + 6853924 = 3762^2 + 2618^2 .

It is not an unprimeable number, because it can be changed into a prime (21006563) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9883 + ... + 11818.

Almost surely, 2^21006568 is an apocalyptic number.

It is an amenable number.

21006568 is an abundant number, since it is smaller than the sum of its proper divisors (22288922).

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

21006568 is a wasteful number, since it uses less digits than its factorization.

21006568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21729 (or 21714 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 21006568 is about 4583.2922664827. The cubic root of 21006568 is about 275.9211775193.

It can be divided in two parts, 2100 and 6568, that added together give a palindrome (8668).

The spelling of 21006568 in words is "twenty-one million, six thousand, five hundred sixty-eight".