21111191 has 2 divisors, whose sum is σ = 21111192. Its totient is φ = 21111190.

The previous prime is 21111179. The next prime is 21111197. The reversal of 21111191 is 19111112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21111191 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111197) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555595 + 10555596.

It is an arithmetic number, because the mean of its divisors is an integer number (10555596).

Almost surely, 2^21111191 is an apocalyptic number.

21111191 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111191 is an equidigital number, since it uses as much as digits as its factorization.

21111191 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18, while the sum is 17.

The square root of 21111191 is about 4594.6916109789. The cubic root of 21111191 is about 276.3784933522.

The spelling of 21111191 in words is "twenty-one million, one hundred eleven thousand, one hundred ninety-one".