21705520211 has 2 divisors, whose sum is σ = 21705520212. Its totient is φ = 21705520210.

The previous prime is 21705520183. The next prime is 21705520223. The reversal of 21705520211 is 11202550712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21705520211 - 2⁶ = 21705520147 is a prime.

It is a super-2 number, since 2×21705520211² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21705520231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10852760105 + 10852760106.

It is an arithmetic number, because the mean of its divisors is an integer number (10852760106).

Almost surely, 2^21705520211 is an apocalyptic number.

21705520211 is a deficient number, since it is larger than the sum of its proper divisors (1).

21705520211 is an equidigital number, since it uses as much as digits as its factorization.

21705520211 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1400, while the sum is 26.

The spelling of 21705520211 in words is "twenty-one billion, seven hundred five million, five hundred twenty thousand, two hundred eleven".