11819981 has 4 divisors (see below), whose sum is σ = 12515292. Its totient is φ = 11124672.

The previous prime is 11819921. The next prime is 11819987. The reversal of 11819981 is 18991811.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4583881 + 7236100 = 2141^2 + 2690^2 .

It is a cyclic number.

It is not a de Polignac number, because 11819981 - 2⁶ = 11819917 is a prime.

It is a super-2 number, since 2×11819981² = 279423901680722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11819987) 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, 347630 + ... + 347663.

It is an arithmetic number, because the mean of its divisors is an integer number (3128823).

Almost surely, 2^11819981 is an apocalyptic number.

It is an amenable number.

11819981 is a deficient number, since it is larger than the sum of its proper divisors (695311).

11819981 is an equidigital number, since it uses as much as digits as its factorization.

11819981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 695310.

The product of its digits is 5184, while the sum is 38.

The square root of 11819981 is about 3438.0199243169. The cubic root of 11819981 is about 227.7922404636.

The spelling of 11819981 in words is "eleven million, eight hundred nineteen thousand, nine hundred eighty-one".