20003121991 has 2 divisors, whose sum is σ = 20003121992. Its totient is φ = 20003121990.

The previous prime is 20003121977. The next prime is 20003122021. The reversal of 20003121991 is 19912130002.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20003121991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20003121191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10001560995 + 10001560996.

It is an arithmetic number, because the mean of its divisors is an integer number (10001560996).

Almost surely, 2^20003121991 is an apocalyptic number.

20003121991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20003121991 is an equidigital number, since it uses as much as digits as its factorization.

20003121991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 972, while the sum is 28.

Adding to 20003121991 its reverse (19912130002), we get a palindrome (39915251993).

The spelling of 20003121991 in words is "twenty billion, three million, one hundred twenty-one thousand, nine hundred ninety-one".