209497678391 has 2 divisors, whose sum is σ = 209497678392. Its totient is φ = 209497678390.

The previous prime is 209497678387. The next prime is 209497678409. The reversal of 209497678391 is 193876794902.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 209497678391 - 2² = 209497678387 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (209497678991) 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 as a sum of consecutive naturals, namely, 104748839195 + 104748839196.

It is an arithmetic number, because the mean of its divisors is an integer number (104748839196).

Almost surely, 2^209497678391 is an apocalyptic number.

209497678391 is a deficient number, since it is larger than the sum of its proper divisors (1).

209497678391 is an equidigital number, since it uses as much as digits as its factorization.

209497678391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 41150592, while the sum is 65.

The spelling of 209497678391 in words is "two hundred nine billion, four hundred ninety-seven million, six hundred seventy-eight thousand, three hundred ninety-one".