665719999 has 4 divisors (see below), whose sum is σ = 760822864. Its totient is φ = 570617136.

The previous prime is 665719979. The next prime is 665720047. The reversal of 665719999 is 999917566.

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

It is a cyclic number.

It is not a de Polignac number, because 665719999 - 2⁷ = 665719871 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665719919) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47551422 + ... + 47551435.

It is an arithmetic number, because the mean of its divisors is an integer number (190205716).

Almost surely, 2^665719999 is an apocalyptic number.

665719999 is a deficient number, since it is larger than the sum of its proper divisors (95102865).

665719999 is an equidigital number, since it uses as much as digits as its factorization.

665719999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95102864.

The product of its digits is 8266860, while the sum is 61.

The square root of 665719999 is about 25801.5503216377. The cubic root of 665719999 is about 873.1667736704.

The spelling of 665719999 in words is "six hundred sixty-five million, seven hundred nineteen thousand, nine hundred ninety-nine".