21021224 has 32 divisors (see below), whose sum is σ = 46502400. Its totient is φ = 8717760.

The previous prime is 21021181. The next prime is 21021229. The reversal of 21021224 is 42212012.

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

It is a junction number, because it is equal to n+sod(n) for n = 21021199 and 21021208.

It is not an unprimeable number, because it can be changed into a prime (21021229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4319 + ... + 7790.

It is an arithmetic number, because the mean of its divisors is an integer number (1453200).

Almost surely, 2^21021224 is an apocalyptic number.

It is an amenable number.

21021224 is an abundant number, since it is smaller than the sum of its proper divisors (25481176).

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

21021224 is a wasteful number, since it uses less digits than its factorization.

21021224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12153 (or 12149 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21021224 is about 4584.8908383952. The cubic root of 21021224 is about 275.9853314335.

Adding to 21021224 its reverse (42212012), we get a palindrome (63233236).

The spelling of 21021224 in words is "twenty-one million, twenty-one thousand, two hundred twenty-four".