21055380 has 48 divisors (see below), whose sum is σ = 60333504. Its totient is φ = 5483520.

The previous prime is 21055379. The next prime is 21055381. The reversal of 21055380 is 8355012.

It is an interprime number because it is at equal distance from previous prime (21055379) and next prime (21055381).

It is a self number, because there is not a number n which added to its sum of digits gives 21055380.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21055381) 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, 1501 + ... + 6660.

It is an arithmetic number, because the mean of its divisors is an integer number (1256948).

Almost surely, 2^21055380 is an apocalyptic number.

21055380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21055380 is an abundant number, since it is smaller than the sum of its proper divisors (39278124).

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

21055380 is a wasteful number, since it uses less digits than its factorization.

21055380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8216 (or 8214 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 21055380 is about 4588.6141698774. The cubic root of 21055380 is about 276.1347273339.

The spelling of 21055380 in words is "twenty-one million, fifty-five thousand, three hundred eighty".