21993211 has 2 divisors, whose sum is σ = 21993212. Its totient is φ = 21993210.

The previous prime is 21993187. The next prime is 21993217. The reversal of 21993211 is 11239912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21993211 - 2¹¹ = 21991163 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21993211.

It is not a weakly prime, because it can be changed into another prime (21993217) 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, 10996605 + 10996606.

It is an arithmetic number, because the mean of its divisors is an integer number (10996606).

Almost surely, 2^21993211 is an apocalyptic number.

21993211 is a deficient number, since it is larger than the sum of its proper divisors (1).

21993211 is an equidigital number, since it uses as much as digits as its factorization.

21993211 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 972, while the sum is 28.

The square root of 21993211 is about 4689.6919941506. The cubic root of 21993211 is about 280.1751073047.

The spelling of 21993211 in words is "twenty-one million, nine hundred ninety-three thousand, two hundred eleven".