1665505999 has 4 divisors (see below), whose sum is σ = 1665679320. Its totient is φ = 1665332680.

The previous prime is 1665505993. The next prime is 1665506027. The reversal of 1665505999 is 9995055661.

It is a happy number.

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 1665505999 - 2⁵ = 1665505967 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 (1665505993) 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, 71344 + ... + 91765.

It is an arithmetic number, because the mean of its divisors is an integer number (416419830).

Almost surely, 2^1665505999 is an apocalyptic number.

1665505999 is a deficient number, since it is larger than the sum of its proper divisors (173321).

1665505999 is a wasteful number, since it uses less digits than its factorization.

1665505999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173320.

The product of its (nonzero) digits is 3280500, while the sum is 55.

The square root of 1665505999 is about 40810.6113529312. The cubic root of 1665505999 is about 1185.3558128462.

The spelling of 1665505999 in words is "one billion, six hundred sixty-five million, five hundred five thousand, nine hundred ninety-nine".