198637661 has 8 divisors (see below), whose sum is σ = 204523704. Its totient is φ = 192801280.

The previous prime is 198637657. The next prime is 198637697. The reversal of 198637661 is 166736891.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 7672900 + 190964761 = 2770^2 + 13819^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 198637661 - 2² = 198637657 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (198637961) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4220 + ... + 20373.

It is an arithmetic number, because the mean of its divisors is an integer number (25565463).

Almost surely, 2^198637661 is an apocalyptic number.

It is an amenable number.

198637661 is a deficient number, since it is larger than the sum of its proper divisors (5886043).

198637661 is a wasteful number, since it uses less digits than its factorization.

198637661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24831.

The product of its digits is 326592, while the sum is 47.

The square root of 198637661 is about 14093.8873629670. The cubic root of 198637661 is about 583.4726867795.

The spelling of 198637661 in words is "one hundred ninety-eight million, six hundred thirty-seven thousand, six hundred sixty-one".