21278208 has 80 divisors (see below), whose sum is σ = 64817280. Its totient is φ = 6076416.

The previous prime is 21278189. The next prime is 21278261. The reversal of 21278208 is 80287212.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9763 + ... + 11741.

It is an arithmetic number, because the mean of its divisors is an integer number (810216).

Almost surely, 2^21278208 is an apocalyptic number.

21278208 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 21278208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32408640).

21278208 is an abundant number, since it is smaller than the sum of its proper divisors (43539072).

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

21278208 is an equidigital number, since it uses as much as digits as its factorization.

21278208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2007 (or 1991 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 21278208 is about 4612.8308011459. The cubic root of 21278208 is about 277.1054176128.

The spelling of 21278208 in words is "twenty-one million, two hundred seventy-eight thousand, two hundred eight".