21222656 has 72 divisors (see below), whose sum is σ = 52195584. Its totient is φ = 8386560.

The previous prime is 21222653. The next prime is 21222671. The reversal of 21222656 is 65622212.

It is a super-2 number, since 2×21222656² = 900802255388672, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21222653) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22841 + ... + 23751.

Almost surely, 2^21222656 is an apocalyptic number.

21222656 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21222656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26097792).

21222656 is an abundant number, since it is smaller than the sum of its proper divisors (30972928).

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

21222656 is an equidigital number, since it uses as much as digits as its factorization.

21222656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 947 (or 933 counting only the distinct ones).

The product of its digits is 2880, while the sum is 26.

The square root of 21222656 is about 4606.8054007088. The cubic root of 21222656 is about 276.8640568111.

Adding to 21222656 its reverse (65622212), we get a palindrome (86844868).

The spelling of 21222656 in words is "twenty-one million, two hundred twenty-two thousand, six hundred fifty-six".