20817216 has 112 divisors (see below), whose sum is σ = 69982080. Its totient is φ = 5944320.

The previous prime is 20817143. The next prime is 20817221. The reversal of 20817216 is 61271802.

It is a tau number, because it is divible by the number of its divisors (112).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 20817216.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11236 + ... + 12956.

It is an arithmetic number, because the mean of its divisors is an integer number (624840).

Almost surely, 2^20817216 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 20817216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34991040).

20817216 is an abundant number, since it is smaller than the sum of its proper divisors (49164864).

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

20817216 is a wasteful number, since it uses less digits than its factorization.

20817216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1749 (or 1733 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 20817216 is about 4562.5887388631. The cubic root of 20817216 is about 275.0896280855.

It can be divided in two parts, 208 and 17216, that added together give a square (17424 = 132²).

The spelling of 20817216 in words is "twenty million, eight hundred seventeen thousand, two hundred sixteen".