11991281 has 4 divisors (see below), whose sum is σ = 12270192. Its totient is φ = 11712372.

The previous prime is 11991271. The next prime is 11991313. The reversal of 11991281 is 18219911.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18219911 = 83 ⋅219517.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-11991281 is a prime.

It is a super-2 number, since 2×11991281² = 287581640041922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11991241) 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, 139391 + ... + 139476.

It is an arithmetic number, because the mean of its divisors is an integer number (3067548).

Almost surely, 2^11991281 is an apocalyptic number.

It is an amenable number.

11991281 is a deficient number, since it is larger than the sum of its proper divisors (278911).

11991281 is an equidigital number, since it uses as much as digits as its factorization.

11991281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278910.

The product of its digits is 1296, while the sum is 32.

The square root of 11991281 is about 3462.8429072079. The cubic root of 11991281 is about 228.8873863899.

The spelling of 11991281 in words is "eleven million, nine hundred ninety-one thousand, two hundred eighty-one".