209973191 has 4 divisors (see below), whose sum is σ = 210121152. Its totient is φ = 209825232.

The previous prime is 209973167. The next prime is 209973209. The reversal of 209973191 is 191379902.

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 209973191 - 2¹⁴ = 209956807 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 (209973691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71831 + ... + 74696.

It is an arithmetic number, because the mean of its divisors is an integer number (52530288).

Almost surely, 2^209973191 is an apocalyptic number.

209973191 is a deficient number, since it is larger than the sum of its proper divisors (147961).

209973191 is a wasteful number, since it uses less digits than its factorization.

209973191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 147960.

The product of its (nonzero) digits is 30618, while the sum is 41.

The square root of 209973191 is about 14490.4517182868. The cubic root of 209973191 is about 594.3669004533.

The spelling of 209973191 in words is "two hundred nine million, nine hundred seventy-three thousand, one hundred ninety-one".