20121819891 has 4 divisors (see below), whose sum is σ = 26829093192. Its totient is φ = 13414546592.

The previous prime is 20121819847. The next prime is 20121819917. The reversal of 20121819891 is 19891812102.

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 20121819891 - 2⁶ = 20121819827 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20121819811) 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, 3353636646 + ... + 3353636651.

It is an arithmetic number, because the mean of its divisors is an integer number (6707273298).

Almost surely, 2^20121819891 is an apocalyptic number.

20121819891 is a deficient number, since it is larger than the sum of its proper divisors (6707273301).

20121819891 is an equidigital number, since it uses as much as digits as its factorization.

20121819891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6707273300.

The product of its (nonzero) digits is 20736, while the sum is 42.

The spelling of 20121819891 in words is "twenty billion, one hundred twenty-one million, eight hundred nineteen thousand, eight hundred ninety-one".