11981999 has 2 divisors, whose sum is σ = 11982000. Its totient is φ = 11981998.

The previous prime is 11981971. The next prime is 11982007. The reversal of 11981999 is 99918911.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 11981999 - 2⁸ = 11981743 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11981909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5990999 + 5991000.

It is an arithmetic number, because the mean of its divisors is an integer number (5991000).

Almost surely, 2^11981999 is an apocalyptic number.

11981999 is a deficient number, since it is larger than the sum of its proper divisors (1).

11981999 is an equidigital number, since it uses as much as digits as its factorization.

11981999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 52488, while the sum is 47.

The square root of 11981999 is about 3461.5024194705. The cubic root of 11981999 is about 228.8283134371.

The spelling of 11981999 in words is "eleven million, nine hundred eighty-one thousand, nine hundred ninety-nine".