198535781 has 2 divisors, whose sum is σ = 198535782. Its totient is φ = 198535780.

The previous prime is 198535723. The next prime is 198535783. The reversal of 198535781 is 187535891.

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., 191822500 + 6713281 = 13850^2 + 2591^2 .

It is a cyclic number.

It is not a de Polignac number, because 198535781 - 2⁶ = 198535717 is a prime.

It is a super-2 number, since 2×198535781² = 78832912674559922, which contains 22 as substring.

Together with 198535783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (198535783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99267890 + 99267891.

It is an arithmetic number, because the mean of its divisors is an integer number (99267891).

Almost surely, 2^198535781 is an apocalyptic number.

It is an amenable number.

198535781 is a deficient number, since it is larger than the sum of its proper divisors (1).

198535781 is an equidigital number, since it uses as much as digits as its factorization.

198535781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 302400, while the sum is 47.

The square root of 198535781 is about 14090.2725665617. The cubic root of 198535781 is about 583.3729165702.

The spelling of 198535781 in words is "one hundred ninety-eight million, five hundred thirty-five thousand, seven hundred eighty-one".