199991678 has 4 divisors (see below), whose sum is σ = 299987520. Its totient is φ = 99995838.

The previous prime is 199991677. The next prime is 199991683. The reversal of 199991678 is 876199991.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (199991677) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49997918 + ... + 49997921.

It is an arithmetic number, because the mean of its divisors is an integer number (74996880).

Almost surely, 2^199991678 is an apocalyptic number.

199991678 is a deficient number, since it is larger than the sum of its proper divisors (99995842).

199991678 is an equidigital number, since it uses as much as digits as its factorization.

199991678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99995841.

The product of its digits is 2204496, while the sum is 59.

The square root of 199991678 is about 14141.8413935385. The cubic root of 199991678 is about 584.7954363049.

The spelling of 199991678 in words is "one hundred ninety-nine million, nine hundred ninety-one thousand, six hundred seventy-eight".