21111099991 has 2 divisors, whose sum is σ = 21111099992. Its totient is φ = 21111099990.

The previous prime is 21111099983. The next prime is 21111100001. The reversal of 21111099991 is 19999011112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21111099991 - 2³ = 21111099983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111099901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555549995 + 10555549996.

It is an arithmetic number, because the mean of its divisors is an integer number (10555549996).

Almost surely, 2^21111099991 is an apocalyptic number.

21111099991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111099991 is an equidigital number, since it uses as much as digits as its factorization.

21111099991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13122, while the sum is 43.

The spelling of 21111099991 in words is "twenty-one billion, one hundred eleven million, ninety-nine thousand, nine hundred ninety-one".