217947 has 4 divisors (see below), whose sum is σ = 290600. Its totient is φ = 145296.

The previous prime is 217937. The next prime is 217969. The reversal of 217947 is 749712.

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

It is not a de Polignac number, because 217947 - 2⁸ = 217691 is a prime.

It is a D-number.

It is a Duffinian number.

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (217907) 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 in 3 ways as a sum of consecutive naturals, for example, 36322 + ... + 36327.

It is an arithmetic number, because the mean of its divisors is an integer number (72650).

2²¹⁷⁹⁴⁷ is an apocalyptic number.

217947 is a deficient number, since it is larger than the sum of its proper divisors (72653).

217947 is an equidigital number, since it uses as much as digits as its factorization.

217947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72652.

The product of its digits is 3528, while the sum is 30.

The square root of 217947 is about 466.8479409829. The cubic root of 217947 is about 60.1797388062.

The spelling of 217947 in words is "two hundred seventeen thousand, nine hundred forty-seven".