21426664 has 64 divisors (see below), whose sum is σ = 49455360. Its totient is φ = 8494080.

The previous prime is 21426659. The next prime is 21426683. The reversal of 21426664 is 46662412.

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 15 ways as a sum of consecutive naturals, for example, 67434 + ... + 67750.

It is an arithmetic number, because the mean of its divisors is an integer number (772740).

Almost surely, 2^21426664 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 21426664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24727680).

21426664 is an abundant number, since it is smaller than the sum of its proper divisors (28028696).

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

21426664 is a wasteful number, since it uses less digits than its factorization.

21426664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 418 (or 414 counting only the distinct ones).

The product of its digits is 13824, while the sum is 31.

The square root of 21426664 is about 4628.8944684449. The cubic root of 21426664 is about 277.7483705521.

The spelling of 21426664 in words is "twenty-one million, four hundred twenty-six thousand, six hundred sixty-four".