211706021 has 2 divisors, whose sum is σ = 211706022. Its totient is φ = 211706020.

The previous prime is 211705993. The next prime is 211706023. The reversal of 211706021 is 120607112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 211557025 + 148996 = 14545^2 + 386^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-211706021 is a prime.

Together with 211706023, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 211705984 and 211706002.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (211706023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 105853010 + 105853011.

It is an arithmetic number, because the mean of its divisors is an integer number (105853011).

Almost surely, 2^211706021 is an apocalyptic number.

It is an amenable number.

211706021 is a deficient number, since it is larger than the sum of its proper divisors (1).

211706021 is an equidigital number, since it uses as much as digits as its factorization.

211706021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 168, while the sum is 20.

The square root of 211706021 is about 14550.1209960605. The cubic root of 211706021 is about 595.9974522435.

The spelling of 211706021 in words is "two hundred eleven million, seven hundred six thousand, twenty-one".