21986191 has 2 divisors, whose sum is σ = 21986192. Its totient is φ = 21986190.

The previous prime is 21986143. The next prime is 21986197. The reversal of 21986191 is 19168912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21986191 - 2¹¹ = 21984143 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21986191.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21986197) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10993095 + 10993096.

It is an arithmetic number, because the mean of its divisors is an integer number (10993096).

Almost surely, 2^21986191 is an apocalyptic number.

21986191 is a deficient number, since it is larger than the sum of its proper divisors (1).

21986191 is an equidigital number, since it uses as much as digits as its factorization.

21986191 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7776, while the sum is 37.

The square root of 21986191 is about 4688.9434844110. The cubic root of 21986191 is about 280.1452944903.

The spelling of 21986191 in words is "twenty-one million, nine hundred eighty-six thousand, one hundred ninety-one".