21816420 has 48 divisors (see below), whose sum is σ = 63745920. Its totient is φ = 5564416.

The previous prime is 21816407. The next prime is 21816451. The reversal of 21816420 is 2461812.

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, 6525 + ... + 9284.

It is an arithmetic number, because the mean of its divisors is an integer number (1328040).

Almost surely, 2^21816420 is an apocalyptic number.

21816420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21816420 is an abundant number, since it is smaller than the sum of its proper divisors (41929500).

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

21816420 is a wasteful number, since it uses less digits than its factorization.

21816420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15844 (or 15842 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21816420 is about 4670.8050697926. The cubic root of 21816420 is about 279.4223635847.

The spelling of 21816420 in words is "twenty-one million, eight hundred sixteen thousand, four hundred twenty".