217121216 has 56 divisors (see below), whose sum is σ = 467130384. Its totient is φ = 99532800.

The previous prime is 217121213. The next prime is 217121221. The reversal of 217121216 is 612121712.

It is a junction number, because it is equal to n+sod(n) for n = 217121191 and 217121200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217121213) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 134816 + ... + 136416.

It is an arithmetic number, because the mean of its divisors is an integer number (8341614).

Almost surely, 2^217121216 is an apocalyptic number.

217121216 is a gapful number since it is divisible by the number (26) 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 217121216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (233565192).

217121216 is an abundant number, since it is smaller than the sum of its proper divisors (250009168).

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

217121216 is a wasteful number, since it uses less digits than its factorization.

217121216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1789 (or 1779 counting only the distinct ones).

The product of its digits is 336, while the sum is 23.

The square root of 217121216 is about 14735.0336273793. The cubic root of 217121216 is about 601.0363718214.

Adding to 217121216 its reverse (612121712), we get a palindrome (829242928).

The spelling of 217121216 in words is "two hundred seventeen million, one hundred twenty-one thousand, two hundred sixteen".