198561556561 has 4 divisors (see below), whose sum is σ = 198586676592. Its totient is φ = 198536436532.

The previous prime is 198561556553. The next prime is 198561556607. The reversal of 198561556561 is 165655165891.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 198561556561 - 2³ = 198561556553 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 198561556496 and 198561556505.

It is not an unprimeable number, because it can be changed into a prime (198561536561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12548155 + ... + 12563968.

It is an arithmetic number, because the mean of its divisors is an integer number (49646669148).

Almost surely, 2^198561556561 is an apocalyptic number.

It is an amenable number.

198561556561 is a deficient number, since it is larger than the sum of its proper divisors (25120031).

198561556561 is an equidigital number, since it uses as much as digits as its factorization.

198561556561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25120030.

The product of its digits is 9720000, while the sum is 58.

The spelling of 198561556561 in words is "one hundred ninety-eight billion, five hundred sixty-one million, five hundred fifty-six thousand, five hundred sixty-one".