21055680 has 112 divisors (see below), whose sum is σ = 74310240. Its totient is φ = 5612544.

The previous prime is 21055679. The next prime is 21055687. The reversal of 21055680 is 8655012.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21055687) 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 15 ways as a sum of consecutive naturals, for example, 7422 + ... + 9858.

Almost surely, 2^21055680 is an apocalyptic number.

21055680 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 21055680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37155120).

21055680 is an abundant number, since it is smaller than the sum of its proper divisors (53254560).

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

21055680 is a wasteful number, since it uses less digits than its factorization.

21055680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2463 (or 2447 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 27.

The square root of 21055680 is about 4588.6468593693. The cubic root of 21055680 is about 276.1360387964.

The spelling of 21055680 in words is "twenty-one million, fifty-five thousand, six hundred eighty".