21220224 has 64 divisors (see below), whose sum is σ = 57213840. Its totient is φ = 6967296.

The previous prime is 21220223. The next prime is 21220231. The reversal of 21220224 is 42202212.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×21220224² = 900595813220352, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220223) 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, 27654 + ... + 28410.

Almost surely, 2^21220224 is an apocalyptic number.

21220224 is a gapful number since it is divisible by the number (24) 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 21220224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28606920).

21220224 is an abundant number, since it is smaller than the sum of its proper divisors (35993616).

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

21220224 is an equidigital number, since it uses as much as digits as its factorization.

21220224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 847 (or 835 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21220224 is about 4606.5414358280. The cubic root of 21220224 is about 276.8534807062.

Adding to 21220224 its reverse (42202212), we get a palindrome (63422436).

It can be divided in two parts, 212202 and 24, that added together give a triangular number (212226 = T₆₅₁).

The spelling of 21220224 in words is "twenty-one million, two hundred twenty thousand, two hundred twenty-four".