21221408 has 48 divisors (see below), whose sum is σ = 45440640. Its totient is φ = 9697536.

The previous prime is 21221383. The next prime is 21221411. The reversal of 21221408 is 80412212.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21221408.

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, 57641 + ... + 58007.

It is an arithmetic number, because the mean of its divisors is an integer number (946680).

Almost surely, 2^21221408 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 21221408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22720320).

21221408 is an abundant number, since it is smaller than the sum of its proper divisors (24219232).

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

21221408 is a wasteful number, since it uses less digits than its factorization.

21221408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 529 (or 521 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 21221408 is about 4606.6699469356. The cubic root of 21221408 is about 276.8586297003.

The spelling of 21221408 in words is "twenty-one million, two hundred twenty-one thousand, four hundred eight".