20010101121991 has 2 divisors, whose sum is σ = 20010101121992. Its totient is φ = 20010101121990.

The previous prime is 20010101121973. The next prime is 20010101122057. The reversal of 20010101121991 is 19912110101002.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20010101121991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20010101121931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10005050560995 + 10005050560996.

It is an arithmetic number, because the mean of its divisors is an integer number (10005050560996).

Almost surely, 2^{20010101121991} is an apocalyptic number.

20010101121991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20010101121991 is an equidigital number, since it uses as much as digits as its factorization.

20010101121991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324, while the sum is 28.

Adding to 20010101121991 its reverse (19912110101002), we get a palindrome (39922211222993).

The spelling of 20010101121991 in words is "twenty trillion, ten billion, one hundred one million, one hundred twenty-one thousand, nine hundred ninety-one".