19997911 has 2 divisors, whose sum is σ = 19997912. Its totient is φ = 19997910.

The previous prime is 19997897. The next prime is 19997953. The reversal of 19997911 is 11979991.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (11979991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19997911 - 2⁹ = 19997399 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19997011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9998955 + 9998956.

It is an arithmetic number, because the mean of its divisors is an integer number (9998956).

Almost surely, 2^19997911 is an apocalyptic number.

19997911 is a deficient number, since it is larger than the sum of its proper divisors (1).

19997911 is an equidigital number, since it uses as much as digits as its factorization.

19997911 is an evil number, because the sum of its binary digits is even.

The product of its digits is 45927, while the sum is 46.

The square root of 19997911 is about 4471.9023916002. The cubic root of 19997911 is about 271.4323106331.

The spelling of 19997911 in words is "nineteen million, nine hundred ninety-seven thousand, nine hundred eleven".