19491917 has 2 divisors, whose sum is σ = 19491918. Its totient is φ = 19491916.

The previous prime is 19491893. The next prime is 19491919. The reversal of 19491917 is 71919491.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17023876 + 2468041 = 4126^2 + 1571^2 .

It is a cyclic number.

It is not a de Polignac number, because 19491917 - 2¹⁸ = 19229773 is a prime.

Together with 19491919, 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 (19491919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9745958 + 9745959.

It is an arithmetic number, because the mean of its divisors is an integer number (9745959).

Almost surely, 2^19491917 is an apocalyptic number.

It is an amenable number.

19491917 is a deficient number, since it is larger than the sum of its proper divisors (1).

19491917 is an equidigital number, since it uses as much as digits as its factorization.

19491917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20412, while the sum is 41.

The square root of 19491917 is about 4414.9651187750. The cubic root of 19491917 is about 269.1234352872.

The spelling of 19491917 in words is "nineteen million, four hundred ninety-one thousand, nine hundred seventeen".