19887191 has 2 divisors, whose sum is σ = 19887192. Its totient is φ = 19887190.

The previous prime is 19887181. The next prime is 19887193. The reversal of 19887191 is 19178891.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19887191 is a prime.

Together with 19887193, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19887193) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9943595 + 9943596.

It is an arithmetic number, because the mean of its divisors is an integer number (9943596).

Almost surely, 2^19887191 is an apocalyptic number.

19887191 is a deficient number, since it is larger than the sum of its proper divisors (1).

19887191 is an equidigital number, since it uses as much as digits as its factorization.

19887191 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 44.

The square root of 19887191 is about 4459.5056900962. The cubic root of 19887191 is about 270.9304478763.

The spelling of 19887191 in words is "nineteen million, eight hundred eighty-seven thousand, one hundred ninety-one".