211981 has 8 divisors (see below), whose sum is σ = 264384. Its totient is φ = 165120.

The previous prime is 211979. The next prime is 211997. The reversal of 211981 is 189112.

211981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 211981 - 2¹ = 211979 is a prime.

It is a super-2 number, since 2×211981² = 89871888722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211931) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1300 + ... + 1453.

It is an arithmetic number, because the mean of its divisors is an integer number (33048).

2²¹¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

211981 is a deficient number, since it is larger than the sum of its proper divisors (52403).

211981 is a wasteful number, since it uses less digits than its factorization.

211981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2771.

The product of its digits is 144, while the sum is 22.

The square root of 211981 is about 460.4139441850. The cubic root of 211981 is about 59.6255382049.

It can be divided in two parts, 21 and 1981, that added together give a palindrome (2002).

The spelling of 211981 in words is "two hundred eleven thousand, nine hundred eighty-one".