217997321 has 8 divisors (see below), whose sum is σ = 229771080. Its totient is φ = 206507392.

The previous prime is 217997309. The next prime is 217997333. The reversal of 217997321 is 123799712.

It is an interprime number because it is at equal distance from previous prime (217997309) and next prime (217997333).

It can be written as a sum of positive squares in 4 ways, for example, as 106399225 + 111598096 = 10315^2 + 10564^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 217997321 - 2⁶ = 217997257 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217990321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 69380 + ... + 72453.

It is an arithmetic number, because the mean of its divisors is an integer number (28721385).

Almost surely, 2^217997321 is an apocalyptic number.

It is an amenable number.

217997321 is a deficient number, since it is larger than the sum of its proper divisors (11773759).

217997321 is a wasteful number, since it uses less digits than its factorization.

217997321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141915.

The product of its digits is 47628, while the sum is 41.

The square root of 217997321 is about 14764.7323375671. The cubic root of 217997321 is about 601.8437001099.

The spelling of 217997321 in words is "two hundred seventeen million, nine hundred ninety-seven thousand, three hundred twenty-one".