21318656 has 44 divisors (see below), whose sum is σ = 43232640. Its totient is φ = 10506240.

The previous prime is 21318653. The next prime is 21318659. The reversal of 21318656 is 65681312.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21318653) and next prime (21318659).

It is a Harshad number since it is a multiple of its sum of digits (32).

Its product of digits (8640) is a multiple of the sum of its prime factors (320).

It is not an unprimeable number, because it can be changed into a prime (21318653) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 111521 + ... + 111711.

It is an arithmetic number, because the mean of its divisors is an integer number (982560).

Almost surely, 2^21318656 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 21318656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21616320).

21318656 is an abundant number, since it is smaller than the sum of its proper divisors (21913984).

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

21318656 is a wasteful number, since it uses less digits than its factorization.

21318656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320 (or 302 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 21318656 is about 4617.2130121969. The cubic root of 21318656 is about 277.2808908072.

Adding to 21318656 its reverse (65681312), we get a palindrome (86999968).

The spelling of 21318656 in words is "twenty-one million, three hundred eighteen thousand, six hundred fifty-six".