21211112001991 has 2 divisors, whose sum is σ = 21211112001992. Its totient is φ = 21211112001990.

The previous prime is 21211112001983. The next prime is 21211112002013. The reversal of 21211112001991 is 19910021111212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21211112001991 - 2³ = 21211112001983 is a prime.

It is a super-2 number, since 2×21211112001991² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21211112001971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605556000995 + 10605556000996.

It is an arithmetic number, because the mean of its divisors is an integer number (10605556000996).

Almost surely, 2^{21211112001991} is an apocalyptic number.

21211112001991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211112001991 is an equidigital number, since it uses as much as digits as its factorization.

21211112001991 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 31.

The spelling of 21211112001991 in words is "twenty-one trillion, two hundred eleven billion, one hundred twelve million, one thousand, nine hundred ninety-one".