197391809 has 2 divisors, whose sum is σ = 197391810. Its totient is φ = 197391808.

The previous prime is 197391797. The next prime is 197391823. The reversal of 197391809 is 908193791.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 185640625 + 11751184 = 13625^2 + 3428^2 .

It is an emirp because it is prime and its reverse (908193791) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 197391809 - 2¹⁶ = 197326273 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (197391899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 98695904 + 98695905.

It is an arithmetic number, because the mean of its divisors is an integer number (98695905).

Almost surely, 2^197391809 is an apocalyptic number.

It is an amenable number.

197391809 is a deficient number, since it is larger than the sum of its proper divisors (1).

197391809 is an equidigital number, since it uses as much as digits as its factorization.

197391809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 122472, while the sum is 47.

The square root of 197391809 is about 14049.6195322151. The cubic root of 197391809 is about 582.2502840181.

The spelling of 197391809 in words is "one hundred ninety-seven million, three hundred ninety-one thousand, eight hundred nine".