999999668 has 6 divisors (see below), whose sum is σ = 1749999426. Its totient is φ = 499999832.

The previous prime is 999999667. The next prime is 999999677. The reversal of 999999668 is 866999999.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 571592464 + 428407204 = 23908^2 + 20698^2 .

It is a super-2 number, since 2×999999668² = 1999998672000220448, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 999999595 and 999999604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999999667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 124999955 + ... + 124999962.

It is an arithmetic number, because the mean of its divisors is an integer number (291666571).

Almost surely, 2^999999668 is an apocalyptic number.

It is an amenable number.

999999668 is a deficient number, since it is larger than the sum of its proper divisors (749999758).

999999668 is a wasteful number, since it uses less digits than its factorization.

999999668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249999921 (or 249999919 counting only the distinct ones).

The product of its digits is 153055008, while the sum is 74.

The square root of 999999668 is about 31622.7713523024. The cubic root of 999999668 is about 999.9998893333. Note that the first 3 decimals are identical.

The spelling of 999999668 in words is "nine hundred ninety-nine million, nine hundred ninety-nine thousand, six hundred sixty-eight".