21055420 has 48 divisors (see below), whose sum is σ = 47295360. Its totient is φ = 7850304.

The previous prime is 21055409. The next prime is 21055429. The reversal of 21055420 is 2455012.

It is a super-2 number, since 2×21055420² = 886661422752800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21055429) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25047 + ... + 25873.

It is an arithmetic number, because the mean of its divisors is an integer number (985320).

Almost surely, 2^21055420 is an apocalyptic number.

21055420 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 21055420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23647680).

21055420 is an abundant number, since it is smaller than the sum of its proper divisors (26239940).

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

21055420 is a wasteful number, since it uses less digits than its factorization.

21055420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 922 (or 920 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21055420 is about 4588.6185284898. The cubic root of 21055420 is about 276.1349021962.

The spelling of 21055420 in words is "twenty-one million, fifty-five thousand, four hundred twenty".