198857509 has 2 divisors, whose sum is σ = 198857510. Its totient is φ = 198857508.

The previous prime is 198857507. The next prime is 198857543. The reversal of 198857509 is 905758891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 115992900 + 82864609 = 10770^2 + 9103^2 .

It is a cyclic number.

It is not a de Polignac number, because 198857509 - 2¹ = 198857507 is a prime.

Together with 198857507, 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 (198857501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99428754 + 99428755.

It is an arithmetic number, because the mean of its divisors is an integer number (99428755).

Almost surely, 2^198857509 is an apocalyptic number.

It is an amenable number.

198857509 is a deficient number, since it is larger than the sum of its proper divisors (1).

198857509 is an equidigital number, since it uses as much as digits as its factorization.

198857509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 907200, while the sum is 52.

The square root of 198857509 is about 14101.6846156762. The cubic root of 198857509 is about 583.6878658608.

The spelling of 198857509 in words is "one hundred ninety-eight million, eight hundred fifty-seven thousand, five hundred nine".