21530208 has 144 divisors (see below), whose sum is σ = 68947200. Its totient is φ = 5854464.

The previous prime is 21530161. The next prime is 21530227. The reversal of 21530208 is 80203512.

It is a Harshad number since it is a multiple of its sum of digits (21).

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, 108093 + ... + 108291.

It is an arithmetic number, because the mean of its divisors is an integer number (478800).

Almost surely, 2^21530208 is an apocalyptic number.

21530208 is a gapful number since it is divisible by the number (28) 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 21530208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34473600).

21530208 is an abundant number, since it is smaller than the sum of its proper divisors (47416992).

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

21530208 is a wasteful number, since it uses less digits than its factorization.

21530208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249 (or 234 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21530208 is about 4640.0655167788. The cubic root of 21530208 is about 278.1950565935.

The spelling of 21530208 in words is "twenty-one million, five hundred thirty thousand, two hundred eight".