211666861 has 8 divisors (see below), whose sum is σ = 252422784. Its totient is φ = 173540400.

The previous prime is 211666843. The next prime is 211666879. The reversal of 211666861 is 168666112.

It is an interprime number because it is at equal distance from previous prime (211666843) and next prime (211666879).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 211666861 - 2⁷ = 211666733 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 211666861.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211666891) 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 in 7 ways as a sum of consecutive naturals, for example, 657190 + ... + 657511.

It is an arithmetic number, because the mean of its divisors is an integer number (31552848).

Almost surely, 2^211666861 is an apocalyptic number.

It is an amenable number.

211666861 is a deficient number, since it is larger than the sum of its proper divisors (40755923).

211666861 is a wasteful number, since it uses less digits than its factorization.

211666861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1314731.

The product of its digits is 20736, while the sum is 37.

The square root of 211666861 is about 14548.7752405486. The cubic root of 211666861 is about 595.9607020694.

The spelling of 211666861 in words is "two hundred eleven million, six hundred sixty-six thousand, eight hundred sixty-one".