217795981 has 8 divisors (see below), whose sum is σ = 235078200. Its totient is φ = 200589312.

The previous prime is 217795967. The next prime is 217796009. The reversal of 217795981 is 189597712.

It can be written as a sum of positive squares in 4 ways, for example, as 70392100 + 147403881 = 8390^2 + 12141^2 .

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 217795981 - 2⁹ = 217795469 is a prime.

It is a super-2 number, since 2×217795981² = 94870178679504722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217795961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12820 + ... + 24493.

It is an arithmetic number, because the mean of its divisors is an integer number (29384775).

Almost surely, 2^217795981 is an apocalyptic number.

It is an amenable number.

217795981 is a deficient number, since it is larger than the sum of its proper divisors (17282219).

217795981 is a wasteful number, since it uses less digits than its factorization.

217795981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37775.

The product of its digits is 317520, while the sum is 49.

The square root of 217795981 is about 14757.9124878826. The cubic root of 217795981 is about 601.6583575645.

The spelling of 217795981 in words is "two hundred seventeen million, seven hundred ninety-five thousand, nine hundred eighty-one".