1205991813 has 16 divisors (see below), whose sum is σ = 1748831616. Its totient is φ = 734798400.

The previous prime is 1205991779. The next prime is 1205991863. The reversal of 1205991813 is 3181995021.

It is not a de Polignac number, because 1205991813 - 2⁹ = 1205991301 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1205991863) 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 15 ways as a sum of consecutive naturals, for example, 149145 + ... + 157022.

It is an arithmetic number, because the mean of its divisors is an integer number (109301976).

Almost surely, 2^1205991813 is an apocalyptic number.

1205991813 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

1205991813 is a deficient number, since it is larger than the sum of its proper divisors (542839803).

1205991813 is a wasteful number, since it uses less digits than its factorization.

1205991813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 306284.

The product of its (nonzero) digits is 19440, while the sum is 39.

The square root of 1205991813 is about 34727.3928333240. The cubic root of 1205991813 is about 1064.4243144948.

The spelling of 1205991813 in words is "one billion, two hundred five million, nine hundred ninety-one thousand, eight hundred thirteen".