999661 has 8 divisors (see below), whose sum is σ = 1086624. Its totient is φ = 914160.

The previous prime is 999653. The next prime is 999667. The reversal of 999661 is 166999.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 999661 - 2³ = 999653 is a prime.

It is a super-2 number, since 2×999661² = 1998644229842, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999667) 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 7 ways as a sum of consecutive naturals, for example, 1410 + ... + 1996.

It is an arithmetic number, because the mean of its divisors is an integer number (135828).

2⁹⁹⁹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

999661 is a deficient number, since it is larger than the sum of its proper divisors (86963).

999661 is a wasteful number, since it uses less digits than its factorization.

999661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 731.

The product of its digits is 26244, while the sum is 40.

The square root of 999661 is about 999.8304856324. The cubic root of 999661 is about 99.9886987229.

The spelling of 999661 in words is "nine hundred ninety-nine thousand, six hundred sixty-one".