191691289 has 2 divisors, whose sum is σ = 191691290. Its totient is φ = 191691288.

The previous prime is 191691287. The next prime is 191691293. The reversal of 191691289 is 982196191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 179560000 + 12131289 = 13400^2 + 3483^2 .

It is a cyclic number.

It is not a de Polignac number, because 191691289 - 2¹ = 191691287 is a prime.

Together with 191691287, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (191691287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95845644 + 95845645.

It is an arithmetic number, because the mean of its divisors is an integer number (95845645).

Almost surely, 2^191691289 is an apocalyptic number.

It is an amenable number.

191691289 is a deficient number, since it is larger than the sum of its proper divisors (1).

191691289 is an equidigital number, since it uses as much as digits as its factorization.

191691289 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69984, while the sum is 46.

The square root of 191691289 is about 13845.2623304869. The cubic root of 191691289 is about 576.5904689918.

The spelling of 191691289 in words is "one hundred ninety-one million, six hundred ninety-one thousand, two hundred eighty-nine".