21305244 has 24 divisors (see below), whose sum is σ = 49935760. Its totient is φ = 7069824.

The previous prime is 21305239. The next prime is 21305257. The reversal of 21305244 is 44250312.

It is a super-3 number, since 3×21305244³ (a number of 23 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21305244.

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, 1129 + ... + 6624.

Almost surely, 2^21305244 is an apocalyptic number.

It is an amenable number.

21305244 is an abundant number, since it is smaller than the sum of its proper divisors (28630516).

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

21305244 is a wasteful number, since it uses less digits than its factorization.

21305244 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7989 (or 7987 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 21305244 is about 4615.7603923947. The cubic root of 21305244 is about 277.2227309267. Note that the first 3 decimals are identical.

Adding to 21305244 its reverse (44250312), we get a palindrome (65555556).

The spelling of 21305244 in words is "twenty-one million, three hundred five thousand, two hundred forty-four".