21000224 has 72 divisors (see below), whose sum is σ = 49124880. Its totient is φ = 8808576.

The previous prime is 21000193. The next prime is 21000229. The reversal of 21000224 is 42200012.

It is not an unprimeable number, because it can be changed into a prime (21000229) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 92399 + ... + 92625.

It is an arithmetic number, because the mean of its divisors is an integer number (682290).

Almost surely, 2^21000224 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 21000224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24562440).

21000224 is an abundant number, since it is smaller than the sum of its proper divisors (28124656).

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

21000224 is a wasteful number, since it uses less digits than its factorization.

21000224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 310 (or 295 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 11.

The square root of 21000224 is about 4582.6001352944. The cubic root of 21000224 is about 275.8933985854.

Adding to 21000224 its reverse (42200012), we get a palindrome (63200236).

The spelling of 21000224 in words is "twenty-one million, two hundred twenty-four", and thus it is an aban number.