21085218 has 96 divisors (see below), whose sum is σ = 58988160. Its totient is φ = 5464800.

The previous prime is 21085213. The next prime is 21085223. The reversal of 21085218 is 81258012.

It is an interprime number because it is at equal distance from previous prime (21085213) and next prime (21085223).

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

It is a junction number, because it is equal to n+sod(n) for n = 21085191 and 21085200.

It is not an unprimeable number, because it can be changed into a prime (21085213) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 45508 + ... + 45968.

It is an arithmetic number, because the mean of its divisors is an integer number (614460).

Almost surely, 2^21085218 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21085218, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29494080).

21085218 is an abundant number, since it is smaller than the sum of its proper divisors (37902942).

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

21085218 is a wasteful number, since it uses less digits than its factorization.

21085218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 501 (or 484 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 21085218 is about 4591.8643272640. The cubic root of 21085218 is about 276.2651044477.

The spelling of 21085218 in words is "twenty-one million, eighty-five thousand, two hundred eighteen".