21208384 has 56 divisors (see below), whose sum is σ = 45235368. Its totient is φ = 9830400.

The previous prime is 21208373. The next prime is 21208387. The reversal of 21208384 is 48380212.

It can be written as a sum of positive squares in 4 ways, for example, as 8761600 + 12446784 = 2960^2 + 3528^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21208387) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 109792 + ... + 109984.

Almost surely, 2^21208384 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 21208384, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22617684).

21208384 is an abundant number, since it is smaller than the sum of its proper divisors (24026984).

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

21208384 is a wasteful number, since it uses less digits than its factorization.

21208384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 323 (or 313 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 28.

The square root of 21208384 is about 4605.2561275134. The cubic root of 21208384 is about 276.8019802280.

Adding to 21208384 its reverse (48380212), we get a palindrome (69588596).

The spelling of 21208384 in words is "twenty-one million, two hundred eight thousand, three hundred eighty-four".