21124220 has 48 divisors (see below), whose sum is σ = 48263040. Its totient is φ = 7719936.

The previous prime is 21124199. The next prime is 21124253. The reversal of 21124220 is 2242112.

It is a junction number, because it is equal to n+sod(n) for n = 21124195 and 21124204.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29021 + ... + 29739.

It is an arithmetic number, because the mean of its divisors is an integer number (1005480).

Almost surely, 2^21124220 is an apocalyptic number.

21124220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21124220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24131520).

21124220 is an abundant number, since it is smaller than the sum of its proper divisors (27138820).

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

21124220 is a wasteful number, since it uses less digits than its factorization.

21124220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 854 (or 852 counting only the distinct ones).

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

The square root of 21124220 is about 4596.1092241155. The cubic root of 21124220 is about 276.4353383191.

Adding to 21124220 its reverse (2242112), we get a palindrome (23366332).

The spelling of 21124220 in words is "twenty-one million, one hundred twenty-four thousand, two hundred twenty".