21643420 has 12 divisors (see below), whose sum is σ = 45451224. Its totient is φ = 8657360.

The previous prime is 21643411. The next prime is 21643421. The reversal of 21643420 is 2434612.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21643391 and 21643400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21643421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 541066 + ... + 541105.

It is an arithmetic number, because the mean of its divisors is an integer number (3787602).

Almost surely, 2^21643420 is an apocalyptic number.

21643420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21643420 is an abundant number, since it is smaller than the sum of its proper divisors (23807804).

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

21643420 is a wasteful number, since it uses less digits than its factorization.

21643420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1082180 (or 1082178 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 22.

The square root of 21643420 is about 4652.2489185339. The cubic root of 21643420 is about 278.6818141788.

The spelling of 21643420 in words is "twenty-one million, six hundred forty-three thousand, four hundred twenty".