198000123781 has 2 divisors, whose sum is σ = 198000123782. Its totient is φ = 198000123780.

The previous prime is 198000123779. The next prime is 198000123791. The reversal of 198000123781 is 187321000891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 109538493156 + 88461630625 = 330966^2 + 297425^2 .

It is an emirp because it is prime and its reverse (187321000891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 198000123781 - 2¹ = 198000123779 is a prime.

It is a super-2 number, since 2×198000123781² (a number of 23 digits) contains 22 as substring.

Together with 198000123779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (198000123731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99000061890 + 99000061891.

It is an arithmetic number, because the mean of its divisors is an integer number (99000061891).

Almost surely, 2^198000123781 is an apocalyptic number.

It is an amenable number.

198000123781 is a deficient number, since it is larger than the sum of its proper divisors (1).

198000123781 is an equidigital number, since it uses as much as digits as its factorization.

198000123781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24192, while the sum is 40.

The spelling of 198000123781 in words is "one hundred ninety-eight billion, one hundred twenty-three thousand, seven hundred eighty-one".