21642224 has 40 divisors (see below), whose sum is σ = 44715888. Its totient is φ = 10112000.

The previous prime is 21642217. The next prime is 21642233. The reversal of 21642224 is 42224612.

It is a self number, because there is not a number n which added to its sum of digits gives 21642224.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 68114 + ... + 68430.

Almost surely, 2^21642224 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 21642224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22357944).

21642224 is an abundant number, since it is smaller than the sum of its proper divisors (23073664).

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

21642224 is a wasteful number, since it uses less digits than its factorization.

21642224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 593 (or 587 counting only the distinct ones).

The product of its digits is 1536, while the sum is 23.

The square root of 21642224 is about 4652.1203767744. The cubic root of 21642224 is about 278.6766808313.

Adding to 21642224 its reverse (42224612), we get a palindrome (63866836).

The spelling of 21642224 in words is "twenty-one million, six hundred forty-two thousand, two hundred twenty-four".