209139197 has 4 divisors (see below), whose sum is σ = 209214720. Its totient is φ = 209063676.

The previous prime is 209139187. The next prime is 209139199. The reversal of 209139197 is 791931902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 791931902 = 2 ⋅395965951.

It is a cyclic number.

It is not a de Polignac number, because 209139197 - 2¹⁴ = 209122813 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 (209139199) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33443 + ... + 39200.

It is an arithmetic number, because the mean of its divisors is an integer number (52303680).

Almost surely, 2^209139197 is an apocalyptic number.

It is an amenable number.

209139197 is a deficient number, since it is larger than the sum of its proper divisors (75523).

209139197 is an equidigital number, since it uses as much as digits as its factorization.

209139197 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75522.

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

The square root of 209139197 is about 14461.6457223927. The cubic root of 209139197 is about 593.5789329231.

The spelling of 209139197 in words is "two hundred nine million, one hundred thirty-nine thousand, one hundred ninety-seven".