21221312 has 84 divisors (see below), whose sum is σ = 50209704. Its totient is φ = 8870400.

The previous prime is 21221303. The next prime is 21221339. The reversal of 21221312 is 21312212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (14).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 210062 + ... + 210162.

Almost surely, 2^21221312 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 21221312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25104852).

21221312 is an abundant number, since it is smaller than the sum of its proper divisors (28988392).

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

21221312 is a wasteful number, since it uses less digits than its factorization.

21221312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 194 (or 177 counting only the distinct ones).

The product of its digits is 48, while the sum is 14.

The square root of 21221312 is about 4606.6595272497. The cubic root of 21221312 is about 276.8582122214.

Adding to 21221312 its reverse (21312212), we get a palindrome (42533524).

The spelling of 21221312 in words is "twenty-one million, two hundred twenty-one thousand, three hundred twelve".