21208320 has 216 divisors, whose sum is σ = 84180096. Its totient is φ = 4829184.

The previous prime is 21208259. The next prime is 21208349. The reversal of 21208320 is 2380212.

It is a happy number.

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

It is a junction number, because it is equal to n+sod(n) for n = 21208293 and 21208302.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 80509 + ... + 80771.

Almost surely, 2^21208320 is an apocalyptic number.

21208320 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 21208320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42090048).

21208320 is an abundant number, since it is smaller than the sum of its proper divisors (62971776).

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

21208320 is a wasteful number, since it uses less digits than its factorization.

21208320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297 (or 280 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21208320 is about 4605.2491789262. The cubic root of 21208320 is about 276.8017017949.

Adding to 21208320 its reverse (2380212), we get a palindrome (23588532).

It can be divided in two parts, 21208 and 320, that added together give a triangular number (21528 = T₂₀₇).

The spelling of 21208320 in words is "twenty-one million, two hundred eight thousand, three hundred twenty".