20201121991 has 2 divisors, whose sum is σ = 20201121992. Its totient is φ = 20201121990.

The previous prime is 20201121971. The next prime is 20201122021. The reversal of 20201121991 is 19912110202.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20201121991 - 2⁵ = 20201121959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20201121901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10100560995 + 10100560996.

It is an arithmetic number, because the mean of its divisors is an integer number (10100560996).

Almost surely, 2^20201121991 is an apocalyptic number.

20201121991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20201121991 is an equidigital number, since it uses as much as digits as its factorization.

20201121991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 28.

The spelling of 20201121991 in words is "twenty billion, two hundred one million, one hundred twenty-one thousand, nine hundred ninety-one".