21243560 has 32 divisors (see below), whose sum is σ = 51476040. Its totient is φ = 7843584.

The previous prime is 21243533. The next prime is 21243581. The reversal of 21243560 is 6534212.

It can be written as a sum of positive squares in 4 ways, for example, as 19377604 + 1865956 = 4402^2 + 1366^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19907 + ... + 20946.

Almost surely, 2^21243560 is an apocalyptic number.

21243560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21243560 is an abundant number, since it is smaller than the sum of its proper divisors (30232480).

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

21243560 is a wasteful number, since it uses less digits than its factorization.

21243560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40877 (or 40873 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 21243560 is about 4609.0736596414. The cubic root of 21243560 is about 276.9549293054.

Adding to 21243560 its reverse (6534212), we get a palindrome (27777772).

The spelling of 21243560 in words is "twenty-one million, two hundred forty-three thousand, five hundred sixty".