21221320 has 16 divisors (see below), whose sum is σ = 47748060. Its totient is φ = 8488512.

The previous prime is 21221303. The next prime is 21221339. The reversal of 21221320 is 2312212.

It can be written as a sum of positive squares in 2 ways, for example, as 21215236 + 6084 = 4606^2 + 78^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21221320.

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 3 ways as a sum of consecutive naturals, for example, 265227 + ... + 265306.

Almost surely, 2^21221320 is an apocalyptic number.

21221320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221320 is an abundant number, since it is smaller than the sum of its proper divisors (26526740).

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

21221320 is a wasteful number, since it uses less digits than its factorization.

21221320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 530544 (or 530540 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21221320 is about 4606.6603955577. The cubic root of 21221320 is about 276.8582470114.

Adding to 21221320 its reverse (2312212), we get a palindrome (23533532).

The spelling of 21221320 in words is "twenty-one million, two hundred twenty-one thousand, three hundred twenty".