21055040 has 56 divisors (see below), whose sum is σ = 52791360. Its totient is φ = 7976448.

The previous prime is 21055037. The next prime is 21055043. The reversal of 21055040 is 4055012.

It is an interprime number because it is at equal distance from previous prime (21055037) and next prime (21055043).

It is not an unprimeable number, because it can be changed into a prime (21055043) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 4349 + ... + 7811.

Almost surely, 2^21055040 is an apocalyptic number.

21055040 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 21055040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26395680).

21055040 is an abundant number, since it is smaller than the sum of its proper divisors (31736320).

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

21055040 is a wasteful number, since it uses less digits than its factorization.

21055040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3499 (or 3489 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 17.

The square root of 21055040 is about 4588.5771215051. The cubic root of 21055040 is about 276.1332409946.

The spelling of 21055040 in words is "twenty-one million, fifty-five thousand, forty".