11991987 has 24 divisors (see below), whose sum is σ = 20962656. Its totient is φ = 6448896.

The previous prime is 11991979. The next prime is 11991997. The reversal of 11991987 is 78919911.

It is not a de Polignac number, because 11991987 - 2³ = 11991979 is a prime.

It is not an unprimeable number, because it can be changed into a prime (11991937) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4528 + ... + 6669.

It is an arithmetic number, because the mean of its divisors is an integer number (873444).

Almost surely, 2^11991987 is an apocalyptic number.

11991987 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

11991987 is a deficient number, since it is larger than the sum of its proper divisors (8970669).

11991987 is a wasteful number, since it uses less digits than its factorization.

11991987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11227 (or 11224 counting only the distinct ones).

The product of its digits is 40824, while the sum is 45.

The square root of 11991987 is about 3462.9448450704. The cubic root of 11991987 is about 228.8918783015.

The spelling of 11991987 in words is "eleven million, nine hundred ninety-one thousand, nine hundred eighty-seven".