198638861 has 2 divisors, whose sum is σ = 198638862. Its totient is φ = 198638860.

The previous prime is 198638851. The next prime is 198638911. The reversal of 198638861 is 168836891.

It is a happy number.

It is an a-pointer prime, because the next prime (198638911) can be obtained adding 198638861 to its sum of digits (50).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 173738761 + 24900100 = 13181^2 + 4990^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-198638861 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (198638851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99319430 + 99319431.

It is an arithmetic number, because the mean of its divisors is an integer number (99319431).

Almost surely, 2^198638861 is an apocalyptic number.

It is an amenable number.

198638861 is a deficient number, since it is larger than the sum of its proper divisors (1).

198638861 is an equidigital number, since it uses as much as digits as its factorization.

198638861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 497664, while the sum is 50.

The square root of 198638861 is about 14093.9299345498. The cubic root of 198638861 is about 583.4738617259.

The spelling of 198638861 in words is "one hundred ninety-eight million, six hundred thirty-eight thousand, eight hundred sixty-one".