999988661 has 8 divisors (see below), whose sum is σ = 1145233920. Its totient is φ = 855340848.

The previous prime is 999988609. The next prime is 999988679. The reversal of 999988661 is 166889999.

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

It is a cyclic number.

It is not a de Polignac number, because 999988661 - 2¹⁴ = 999972277 is a prime.

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 (999988261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 145766 + ... + 152471.

It is an arithmetic number, because the mean of its divisors is an integer number (143154240).

Almost surely, 2^999988661 is an apocalyptic number.

It is an amenable number.

999988661 is a deficient number, since it is larger than the sum of its proper divisors (145245259).

999988661 is a wasteful number, since it uses less digits than its factorization.

999988661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 298723.

The product of its digits is 15116544, while the sum is 65.

The square root of 999988661 is about 31622.5973158436. The cubic root of 999988661 is about 999.9962203190.

The spelling of 999988661 in words is "nine hundred ninety-nine million, nine hundred eighty-eight thousand, six hundred sixty-one".