1311999978 has 16 divisors (see below), whose sum is σ = 2624971680. Its totient is φ = 437171376.

The previous prime is 1311999967. The next prime is 1311999979. The reversal of 1311999978 is 8799991131.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1311999979) 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 7 ways as a sum of consecutive naturals, for example, 22308 + ... + 55871.

It is an arithmetic number, because the mean of its divisors is an integer number (164060730).

Almost surely, 2^1311999978 is an apocalyptic number.

1311999978 is an abundant number, since it is smaller than the sum of its proper divisors (1312971702).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1311999978 is a wasteful number, since it uses less digits than its factorization.

1311999978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80981.

The product of its digits is 1102248, while the sum is 57.

The square root of 1311999978 is about 36221.5402488630. The cubic root of 1311999978 is about 1094.7407288407.

The spelling of 1311999978 in words is "one billion, three hundred eleven million, nine hundred ninety-nine thousand, nine hundred seventy-eight".