2011981 has 4 divisors (see below), whose sum is σ = 2016352. Its totient is φ = 2007612.

The previous prime is 2011973. The next prime is 2011987. The reversal of 2011981 is 1891102.

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 2011981 - 2³ = 2011973 is a prime.

It is a super-2 number, since 2×2011981² = 8096135088722, 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 (2011987) 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 3 ways as a sum of consecutive naturals, for example, 1401 + ... + 2446.

It is an arithmetic number, because the mean of its divisors is an integer number (504088).

2^2011981 is an apocalyptic number.

It is an amenable number.

2011981 is a deficient number, since it is larger than the sum of its proper divisors (4371).

2011981 is an equidigital number, since it uses as much as digits as its factorization.

2011981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4370.

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

The square root of 2011981 is about 1418.4431606518. The cubic root of 2011981 is about 126.2431895160.

It can be divided in two parts, 2011 and 981, that multiplied together give a palindrome (1972791).

The spelling of 2011981 in words is "two million, eleven thousand, nine hundred eighty-one".