20198866691 has 4 divisors (see below), whose sum is σ = 20202073584. Its totient is φ = 20195659800.

The previous prime is 20198866673. The next prime is 20198866697. The reversal of 20198866691 is 19666889102.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20198866691 - 2²⁶ = 20131757827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20198866697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1593980 + ... + 1606601.

It is an arithmetic number, because the mean of its divisors is an integer number (5050518396).

Almost surely, 2^20198866691 is an apocalyptic number.

20198866691 is a deficient number, since it is larger than the sum of its proper divisors (3206893).

20198866691 is an equidigital number, since it uses as much as digits as its factorization.

20198866691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3206892.

The product of its (nonzero) digits is 2239488, while the sum is 56.

The spelling of 20198866691 in words is "twenty billion, one hundred ninety-eight million, eight hundred sixty-six thousand, six hundred ninety-one".