21210084 has 72 divisors (see below), whose sum is σ = 64891008. Its totient is φ = 5702400.

The previous prime is 21210053. The next prime is 21210089. The reversal of 21210084 is 48001212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210089) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1809 + ... + 6759.

It is an arithmetic number, because the mean of its divisors is an integer number (901264).

Almost surely, 2^21210084 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21210084, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32445504).

21210084 is an abundant number, since it is smaller than the sum of its proper divisors (43680924).

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

21210084 is a wasteful number, since it uses less digits than its factorization.

21210084 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4985 (or 4980 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 21210084 is about 4605.4406955252. The cubic root of 21210084 is about 276.8093759006.

Adding to 21210084 its reverse (48001212), we get a palindrome (69211296).

It can be divided in two parts, 212 and 10084, that added together give a triangular number (10296 = T₁₄₃).

The spelling of 21210084 in words is "twenty-one million, two hundred ten thousand, eighty-four".