217720313 has 4 divisors (see below), whose sum is σ = 225227940. Its totient is φ = 210212688.

The previous prime is 217720289. The next prime is 217720331. The reversal of 217720313 is 313027712.

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

It can be written as a sum of positive squares in 2 ways, for example, as 183521209 + 34199104 = 13547^2 + 5848^2 .

It is a cyclic number.

It is not a de Polignac number, because 217720313 - 2⁸ = 217720057 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (217720213) 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 3 ways as a sum of consecutive naturals, for example, 3753770 + ... + 3753827.

It is an arithmetic number, because the mean of its divisors is an integer number (56306985).

Almost surely, 2^217720313 is an apocalyptic number.

It is an amenable number.

217720313 is a deficient number, since it is larger than the sum of its proper divisors (7507627).

217720313 is an equidigital number, since it uses as much as digits as its factorization.

217720313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7507626.

The product of its (nonzero) digits is 1764, while the sum is 26.

The square root of 217720313 is about 14755.3486234653. The cubic root of 217720313 is about 601.5886722290.

The spelling of 217720313 in words is "two hundred seventeen million, seven hundred twenty thousand, three hundred thirteen".