999666 has 48 divisors (see below), whose sum is σ = 2371200. Its totient is φ = 303264.

The previous prime is 999653. The next prime is 999667. The reversal of 999666 is 666999.

999666 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×999666² = 1998664223112, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

999666 is a strobogrammatic number because it is the same when read upside-down.

It is a nialpdrome in base 10.

It is a zygodrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (999667) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12615 + ... + 12693.

It is an arithmetic number, because the mean of its divisors is an integer number (49400).

2⁹⁹⁹⁶⁶⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 999666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1185600).

999666 is an abundant number, since it is smaller than the sum of its proper divisors (1371534).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

999666 is a wasteful number, since it uses less digits than its factorization.

999666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143 (or 140 counting only the distinct ones).

The product of its digits is 157464, while the sum is 45.

The square root of 999666 is about 999.8329860532. The cubic root of 999666 is about 99.9888654269.

The spelling of 999666 in words is "nine hundred ninety-nine thousand, six hundred sixty-six".