199689991 has 4 divisors (see below), whose sum is σ = 199748032. Its totient is φ = 199631952.

The previous prime is 199689989. The next prime is 199690009. The reversal of 199689991 is 199986991.

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

It is a cyclic number.

It is not a de Polignac number, because 199689991 - 2¹ = 199689989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (199689961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23511 + ... + 30856.

It is an arithmetic number, because the mean of its divisors is an integer number (49937008).

Almost surely, 2^199689991 is an apocalyptic number.

199689991 is a deficient number, since it is larger than the sum of its proper divisors (58041).

199689991 is an equidigital number, since it uses as much as digits as its factorization.

199689991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58040.

The product of its digits is 2834352, while the sum is 61.

The square root of 199689991 is about 14131.1708998228. The cubic root of 199689991 is about 584.5012341172.

The spelling of 199689991 in words is "one hundred ninety-nine million, six hundred eighty-nine thousand, nine hundred ninety-one".