197638289821 has 4 divisors (see below), whose sum is σ = 225872331232. Its totient is φ = 169404248412.

The previous prime is 197638289819. The next prime is 197638289839. The reversal of 197638289821 is 128982836791.

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, and also an emirpimes, since its reverse is a distinct semiprime: 128982836791 = 100069 ⋅1288939.

It is not a de Polignac number, because 197638289821 - 2¹ = 197638289819 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 (197638289881) 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, 14117020695 + ... + 14117020708.

It is an arithmetic number, because the mean of its divisors is an integer number (56468082808).

Almost surely, 2^197638289821 is an apocalyptic number.

It is an amenable number.

197638289821 is a deficient number, since it is larger than the sum of its proper divisors (28234041411).

197638289821 is an equidigital number, since it uses as much as digits as its factorization.

197638289821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28234041410.

The product of its digits is 20901888, while the sum is 64.

The spelling of 197638289821 in words is "one hundred ninety-seven billion, six hundred thirty-eight million, two hundred eighty-nine thousand, eight hundred twenty-one".