217121218 has 4 divisors (see below), whose sum is σ = 325681830. Its totient is φ = 108560608.

The previous prime is 217121213. The next prime is 217121221. The reversal of 217121218 is 812121712.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 194965369 + 22155849 = 13963^2 + 4707^2 .

It is a junction number, because it is equal to n+sod(n) for n = 217121192 and 217121201.

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

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 as a sum of consecutive naturals, namely, 54280303 + ... + 54280306.

Almost surely, 2^217121218 is an apocalyptic number.

217121218 is a deficient number, since it is larger than the sum of its proper divisors (108560612).

217121218 is a wasteful number, since it uses less digits than its factorization.

217121218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108560611.

The product of its digits is 448, while the sum is 25.

The square root of 217121218 is about 14735.0336952448. The cubic root of 217121218 is about 601.0363736668.

The spelling of 217121218 in words is "two hundred seventeen million, one hundred twenty-one thousand, two hundred eighteen".