19891812197 has 2 divisors, whose sum is σ = 19891812198. Its totient is φ = 19891812196.

The previous prime is 19891812137. The next prime is 19891812203. The reversal of 19891812197 is 79121819891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10644874276 + 9246937921 = 103174^2 + 96161^2 .

It is an emirp because it is prime and its reverse (79121819891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19891812197 - 2⁸ = 19891811941 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19891812137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9945906098 + 9945906099.

It is an arithmetic number, because the mean of its divisors is an integer number (9945906099).

Almost surely, 2^19891812197 is an apocalyptic number.

It is an amenable number.

19891812197 is a deficient number, since it is larger than the sum of its proper divisors (1).

19891812197 is an equidigital number, since it uses as much as digits as its factorization.

19891812197 is an evil number, because the sum of its binary digits is even.

The product of its digits is 653184, while the sum is 56.

The spelling of 19891812197 in words is "nineteen billion, eight hundred ninety-one million, eight hundred twelve thousand, one hundred ninety-seven".