669999 has 16 divisors (see below), whose sum is σ = 990720. Its totient is φ = 399360.

The previous prime is 669989. The next prime is 670001. The reversal of 669999 is 999966.

669999 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 669999 - 2¹⁷ = 538927 is a prime.

669999 is a modest number, since divided by 999 gives 669 as remainder.

669999 is strictly pandigital in base 7.

It is a plaindrome in base 10.

It is a zygodrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (669989) 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 15 ways as a sum of consecutive naturals, for example, 2479 + ... + 2735.

It is an arithmetic number, because the mean of its divisors is an integer number (61920).

2⁶⁶⁹⁹⁹⁹ is an apocalyptic number.

669999 is a deficient number, since it is larger than the sum of its proper divisors (320721).

669999 is a wasteful number, since it uses less digits than its factorization.

669999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350.

The product of its digits is 236196, while the sum is 48.

The square root of 669999 is about 818.5346663398. The cubic root of 669999 is about 87.5033576943.

The spelling of 669999 in words is "six hundred sixty-nine thousand, nine hundred ninety-nine".