21055620 has 48 divisors (see below), whose sum is σ = 59633280. Its totient is φ = 5550336.

The previous prime is 21055607. The next prime is 21055631. The reversal of 21055620 is 2655012.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3369 + ... + 7311.

It is an arithmetic number, because the mean of its divisors is an integer number (1242360).

Almost surely, 2^21055620 is an apocalyptic number.

21055620 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 21055620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29816640).

21055620 is an abundant number, since it is smaller than the sum of its proper divisors (38577660).

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

21055620 is a wasteful number, since it uses less digits than its factorization.

21055620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4044 (or 4042 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21055620 is about 4588.6403214896. The cubic root of 21055620 is about 276.1357765049.

The spelling of 21055620 in words is "twenty-one million, fifty-five thousand, six hundred twenty".