211561 has 4 divisors (see below), whose sum is σ = 241792. Its totient is φ = 181332.

The previous prime is 211559. The next prime is 211571. The reversal of 211561 is 165112.

It is a happy number.

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 211561 - 2¹ = 211559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (211501) 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, 15105 + ... + 15118.

It is an arithmetic number, because the mean of its divisors is an integer number (60448).

2²¹¹⁵⁶¹ is an apocalyptic number.

It is an amenable number.

211561 is a deficient number, since it is larger than the sum of its proper divisors (30231).

211561 is an equidigital number, since it uses as much as digits as its factorization.

211561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30230.

The product of its digits is 60, while the sum is 16.

The square root of 211561 is about 459.9576067422. The cubic root of 211561 is about 59.5861332843.

Adding to 211561 its reverse (165112), we get a palindrome (376673).

The spelling of 211561 in words is "two hundred eleven thousand, five hundred sixty-one".