19919197 has 2 divisors, whose sum is σ = 19919198. Its totient is φ = 19919196.

The previous prime is 19919183. The next prime is 19919203. The reversal of 19919197 is 79191991.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14485636 + 5433561 = 3806^2 + 2331^2 .

It is an emirp because it is prime and its reverse (79191991) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19919197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19919147) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9959598 + 9959599.

It is an arithmetic number, because the mean of its divisors is an integer number (9959599).

Almost surely, 2^19919197 is an apocalyptic number.

It is an amenable number.

19919197 is a deficient number, since it is larger than the sum of its proper divisors (1).

19919197 is an equidigital number, since it uses as much as digits as its factorization.

19919197 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 19919197 is about 4463.0927617517. The cubic root of 19919197 is about 271.0757131079.

The spelling of 19919197 in words is "nineteen million, nine hundred nineteen thousand, one hundred ninety-seven".