991888166 has 4 divisors (see below), whose sum is σ = 1487832252. Its totient is φ = 495944082.

The previous prime is 991888153. The next prime is 991888199. The reversal of 991888166 is 661888199.

991888166 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

991888166 is a strobogrammatic number because it is the same when read upside-down.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 247972040 + ... + 247972043.

It is an arithmetic number, because the mean of its divisors is an integer number (371958063).

Almost surely, 2^991888166 is an apocalyptic number.

991888166 is a deficient number, since it is larger than the sum of its proper divisors (495944086).

991888166 is a wasteful number, since it uses less digits than its factorization.

991888166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 495944085.

The product of its digits is 1492992, while the sum is 56.

The square root of 991888166 is about 31494.2560794822. The cubic root of 991888166 is about 997.2887108883.

The spelling of 991888166 in words is "nine hundred ninety-one million, eight hundred eighty-eight thousand, one hundred sixty-six".