21424820 has 12 divisors (see below), whose sum is σ = 44992164. Its totient is φ = 8569920.

The previous prime is 21424787. The next prime is 21424829. The reversal of 21424820 is 2842412.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 17073424 + 4351396 = 4132^2 + 2086^2 .

It is a hoax number, since the sum of its digits (23) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21424829) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 535601 + ... + 535640.

It is an arithmetic number, because the mean of its divisors is an integer number (3749347).

Almost surely, 2^21424820 is an apocalyptic number.

21424820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21424820 is an abundant number, since it is smaller than the sum of its proper divisors (23567344).

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

21424820 is a wasteful number, since it uses less digits than its factorization.

21424820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1071250 (or 1071248 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 23.

The square root of 21424820 is about 4628.6952805299. The cubic root of 21424820 is about 277.7404025565.

The spelling of 21424820 in words is "twenty-one million, four hundred twenty-four thousand, eight hundred twenty".