211540661 has 4 divisors (see below), whose sum is σ = 222674400. Its totient is φ = 200406924.

The previous prime is 211540657. The next prime is 211540663. The reversal of 211540661 is 166045112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 211540661 - 2² = 211540657 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 211540661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211540663) 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 3 ways as a sum of consecutive naturals, for example, 5566841 + ... + 5566878.

It is an arithmetic number, because the mean of its divisors is an integer number (55668600).

Almost surely, 2^211540661 is an apocalyptic number.

It is an amenable number.

211540661 is a deficient number, since it is larger than the sum of its proper divisors (11133739).

211540661 is a wasteful number, since it uses less digits than its factorization.

211540661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11133738.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 211540661 is about 14544.4374590425. The cubic root of 211540661 is about 595.8422373075.

Adding to 211540661 its reverse (166045112), we get a palindrome (377585773).

The spelling of 211540661 in words is "two hundred eleven million, five hundred forty thousand, six hundred sixty-one".