21220416 has 168 divisors, whose sum is σ = 73436480. Its totient is φ = 5723136.

The previous prime is 21220393. The next prime is 21220417. The reversal of 21220416 is 61402212.

It is a tau number, because it is divible by the number of its divisors (168).

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

It is not an unprimeable number, because it can be changed into a prime (21220417) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 76470 + ... + 76746.

Almost surely, 2^21220416 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 21220416, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36718240).

21220416 is an abundant number, since it is smaller than the sum of its proper divisors (52216064).

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

21220416 is a wasteful number, since it uses less digits than its factorization.

21220416 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 321 (or 308 counting only the distinct ones).

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

The square root of 21220416 is about 4606.5622757106. The cubic root of 21220416 is about 276.8543156912.

Adding to 21220416 its reverse (61402212), we get a palindrome (82622628).

The spelling of 21220416 in words is "twenty-one million, two hundred twenty thousand, four hundred sixteen".