217998121 has 4 divisors (see below), whose sum is σ = 237816144. Its totient is φ = 198180100.

The previous prime is 217998119. The next prime is 217998139. The reversal of 217998121 is 121899712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 217998121 - 2¹ = 217998119 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217998721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9908995 + ... + 9909016.

It is an arithmetic number, because the mean of its divisors is an integer number (59454036).

Almost surely, 2^217998121 is an apocalyptic number.

It is an amenable number.

217998121 is a deficient number, since it is larger than the sum of its proper divisors (19818023).

217998121 is a wasteful number, since it uses less digits than its factorization.

217998121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19818022.

The product of its digits is 18144, while the sum is 40.

The square root of 217998121 is about 14764.7594291272. The cubic root of 217998121 is about 601.8444363183.

The spelling of 217998121 in words is "two hundred seventeen million, nine hundred ninety-eight thousand, one hundred twenty-one".