21131191 has 2 divisors, whose sum is σ = 21131192. Its totient is φ = 21131190.

The previous prime is 21131183. The next prime is 21131251. The reversal of 21131191 is 19113112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21131191 - 2³ = 21131183 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21131141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10565595 + 10565596.

It is an arithmetic number, because the mean of its divisors is an integer number (10565596).

Almost surely, 2^21131191 is an apocalyptic number.

21131191 is a deficient number, since it is larger than the sum of its proper divisors (1).

21131191 is an equidigital number, since it uses as much as digits as its factorization.

21131191 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54, while the sum is 19.

The square root of 21131191 is about 4596.8675203882. The cubic root of 21131191 is about 276.4657428943.

It can be divided in two parts, 211311 and 91, that multiplied together give a triangular number (19229301 = T₆₂₀₁).

The spelling of 21131191 in words is "twenty-one million, one hundred thirty-one thousand, one hundred ninety-one".