21218200 has 48 divisors (see below), whose sum is σ = 49639680. Its totient is φ = 8434560.

The previous prime is 21218191. The next prime is 21218233. The reversal of 21218200 is 281212.

21218200 = T₃₅₇ + T₃₅₈ + ... + T₅₅₆.

It is a super-2 number, since 2×21218200² = 900424022480000, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 55209 + ... + 55591.

It is an arithmetic number, because the mean of its divisors is an integer number (1034160).

Almost surely, 2^21218200 is an apocalyptic number.

21218200 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 21218200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24819840).

21218200 is an abundant number, since it is smaller than the sum of its proper divisors (28421480).

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

21218200 is a wasteful number, since it uses less digits than its factorization.

21218200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 676 (or 667 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 21218200 is about 4606.3217429962. The cubic root of 21218200 is about 276.8446782659.

Adding to 21218200 its reverse (281212), we get a palindrome (21499412).

It can be divided in two parts, 21218 and 200, that multiplied together give a square (4243600 = 2060²).

The spelling of 21218200 in words is "twenty-one million, two hundred eighteen thousand, two hundred".