211691661 has 8 divisors (see below), whose sum is σ = 282869664. Its totient is φ = 140820720.

The previous prime is 211691617. The next prime is 211691681. The reversal of 211691661 is 166196112.

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

It is not a de Polignac number, because 211691661 - 2¹⁰ = 211690637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211691611) 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 in 7 ways as a sum of consecutive naturals, for example, 75151 + ... + 77916.

It is an arithmetic number, because the mean of its divisors is an integer number (35358708).

Almost surely, 2^211691661 is an apocalyptic number.

It is an amenable number.

211691661 is a deficient number, since it is larger than the sum of its proper divisors (71178003).

211691661 is a wasteful number, since it uses less digits than its factorization.

211691661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 153531.

The product of its digits is 3888, while the sum is 33.

The square root of 211691661 is about 14549.6275210055. The cubic root of 211691661 is about 595.9839764546.

The spelling of 211691661 in words is "two hundred eleven million, six hundred ninety-one thousand, six hundred sixty-one".