19997399 has 2 divisors, whose sum is σ = 19997400. Its totient is φ = 19997398.

The previous prime is 19997357. The next prime is 19997413. The reversal of 19997399 is 99379991.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (99379991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19997399 - 2²⁰ = 18948823 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19997339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9998699 + 9998700.

It is an arithmetic number, because the mean of its divisors is an integer number (9998700).

Almost surely, 2^19997399 is an apocalyptic number.

19997399 is a deficient number, since it is larger than the sum of its proper divisors (1).

19997399 is an equidigital number, since it uses as much as digits as its factorization.

19997399 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1240029, while the sum is 56.

The square root of 19997399 is about 4471.8451449038. The cubic root of 19997399 is about 271.4299941490.

The spelling of 19997399 in words is "nineteen million, nine hundred ninety-seven thousand, three hundred ninety-nine".