11861981 has 4 divisors (see below), whose sum is σ = 11891964. Its totient is φ = 11832000.

The previous prime is 11861959. The next prime is 11861987. The reversal of 11861981 is 18916811.

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 10725625 + 1136356 = 3275^2 + 1066^2 .

It is a cyclic number.

It is not a de Polignac number, because 11861981 - 2⁶ = 11861917 is a prime.

It is a super-2 number, since 2×11861981² = 281413186488722, 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 (11861987) 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, 14390 + ... + 15191.

It is an arithmetic number, because the mean of its divisors is an integer number (2972991).

Almost surely, 2^11861981 is an apocalyptic number.

It is an amenable number.

11861981 is a deficient number, since it is larger than the sum of its proper divisors (29983).

11861981 is an equidigital number, since it uses as much as digits as its factorization.

11861981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29982.

The product of its digits is 3456, while the sum is 35.

The square root of 11861981 is about 3444.1226749348. The cubic root of 11861981 is about 228.0617266441.

The spelling of 11861981 in words is "eleven million, eight hundred sixty-one thousand, nine hundred eighty-one".