211221009491 has 2 divisors, whose sum is σ = 211221009492. Its totient is φ = 211221009490.

The previous prime is 211221009409. The next prime is 211221009533. The reversal of 211221009491 is 194900122112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 211221009491 - 2²⁶ = 211153900627 is a prime.

It is a super-2 number, since 2×211221009491² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (211221209491) 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, 105610504745 + 105610504746.

It is an arithmetic number, because the mean of its divisors is an integer number (105610504746).

Almost surely, 2^211221009491 is an apocalyptic number.

211221009491 is a deficient number, since it is larger than the sum of its proper divisors (1).

211221009491 is an equidigital number, since it uses as much as digits as its factorization.

211221009491 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 32.

The spelling of 211221009491 in words is "two hundred eleven billion, two hundred twenty-one million, nine thousand, four hundred ninety-one".