198397821637 has 4 divisors (see below), whose sum is σ = 201760496640. Its totient is φ = 195035146636.

The previous prime is 198397821563. The next prime is 198397821641. The reversal of 198397821637 is 736128793891.

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 198397821637 - 2³¹ = 196250337989 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 (198397821137) 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, 1681337413 + ... + 1681337530.

It is an arithmetic number, because the mean of its divisors is an integer number (50440124160).

Almost surely, 2^198397821637 is an apocalyptic number.

It is an amenable number.

198397821637 is a deficient number, since it is larger than the sum of its proper divisors (3362675003).

198397821637 is an equidigital number, since it uses as much as digits as its factorization.

198397821637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3362675002.

The product of its digits is 27433728, while the sum is 64.

The spelling of 198397821637 in words is "one hundred ninety-eight billion, three hundred ninety-seven million, eight hundred twenty-one thousand, six hundred thirty-seven".