211705786261 has 4 divisors (see below), whose sum is σ = 211851490252. Its totient is φ = 211560082272.

The previous prime is 211705786213. The next prime is 211705786289. The reversal of 211705786261 is 162687507112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 169224454161 + 42481332100 = 411369^2 + 206110^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-211705786261 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211705736261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 72849816 + ... + 72852721.

It is an arithmetic number, because the mean of its divisors is an integer number (52962872563).

Almost surely, 2^211705786261 is an apocalyptic number.

It is an amenable number.

211705786261 is a deficient number, since it is larger than the sum of its proper divisors (145703991).

211705786261 is a wasteful number, since it uses less digits than its factorization.

211705786261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145703990.

The product of its (nonzero) digits is 282240, while the sum is 46.

The spelling of 211705786261 in words is "two hundred eleven billion, seven hundred five million, seven hundred eighty-six thousand, two hundred sixty-one".