665751217 has 4 divisors (see below), whose sum is σ = 673772400. Its totient is φ = 657730036.

The previous prime is 665751197. The next prime is 665751259. The reversal of 665751217 is 712157566.

It is a happy number.

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 665751217 - 2¹⁹ = 665226929 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 665751217.

It is not an unprimeable number, because it can be changed into a prime (665751277) 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, 4010467 + ... + 4010632.

It is an arithmetic number, because the mean of its divisors is an integer number (168443100).

Almost surely, 2^665751217 is an apocalyptic number.

It is an amenable number.

665751217 is a deficient number, since it is larger than the sum of its proper divisors (8021183).

665751217 is an equidigital number, since it uses as much as digits as its factorization.

665751217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8021182.

The product of its digits is 88200, while the sum is 40.

The square root of 665751217 is about 25802.1552781933. The cubic root of 665751217 is about 873.1804220983.

The spelling of 665751217 in words is "six hundred sixty-five million, seven hundred fifty-one thousand, two hundred seventeen".