21112009991 has 2 divisors, whose sum is σ = 21112009992. Its totient is φ = 21112009990.

The previous prime is 21112009979. The next prime is 21112010039. The reversal of 21112009991 is 19990021112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21112009991 - 2⁶ = 21112009927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21112009291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556004995 + 10556004996.

It is an arithmetic number, because the mean of its divisors is an integer number (10556004996).

Almost surely, 2^21112009991 is an apocalyptic number.

21112009991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21112009991 is an equidigital number, since it uses as much as digits as its factorization.

21112009991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2916, while the sum is 35.

It can be divided in two parts, 2111 and 2009991, that added together give a palindrome (2012102).

The spelling of 21112009991 in words is "twenty-one billion, one hundred twelve million, nine thousand, nine hundred ninety-one".