209197861 has 4 divisors (see below), whose sum is σ = 210136192. Its totient is φ = 208259532.

The previous prime is 209197843. The next prime is 209197871. The reversal of 209197861 is 168791902.

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.

It is a cyclic number.

It is not a de Polignac number, because 209197861 - 2¹¹ = 209195813 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 (209197831) 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, 468831 + ... + 469276.

It is an arithmetic number, because the mean of its divisors is an integer number (52534048).

Almost surely, 2^209197861 is an apocalyptic number.

It is an amenable number.

209197861 is a deficient number, since it is larger than the sum of its proper divisors (938331).

209197861 is an equidigital number, since it uses as much as digits as its factorization.

209197861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 938330.

The product of its (nonzero) digits is 54432, while the sum is 43.

The square root of 209197861 is about 14463.6738417319. The cubic root of 209197861 is about 593.6344277955.

The spelling of 209197861 in words is "two hundred nine million, one hundred ninety-seven thousand, eight hundred sixty-one".