209996191 has 4 divisors (see below), whose sum is σ = 210077712. Its totient is φ = 209914672.

The previous prime is 209996161. The next prime is 209996197. The reversal of 209996191 is 191699902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 191699902 = 2 ⋅95849951.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-209996191 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 (209996197) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36766 + ... + 42091.

It is an arithmetic number, because the mean of its divisors is an integer number (52519428).

Almost surely, 2^209996191 is an apocalyptic number.

209996191 is a deficient number, since it is larger than the sum of its proper divisors (81521).

209996191 is an equidigital number, since it uses as much as digits as its factorization.

209996191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81520.

The product of its (nonzero) digits is 78732, while the sum is 46.

The square root of 209996191 is about 14491.2453226077. The cubic root of 209996191 is about 594.3886015405.

The spelling of 209996191 in words is "two hundred nine million, nine hundred ninety-six thousand, one hundred ninety-one".