1218534391 has 16 divisors (see below), whose sum is σ = 1356364800. Its totient is φ = 1089892800.

The previous prime is 1218534379. The next prime is 1218534433. The reversal of 1218534391 is 1934358121.

It is a cyclic number.

It is not a de Polignac number, because 1218534391 - 2⁷ = 1218534263 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1218534391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1218514391) 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, 1081 + ... + 49378.

It is an arithmetic number, because the mean of its divisors is an integer number (84772800).

Almost surely, 2^1218534391 is an apocalyptic number.

1218534391 is a deficient number, since it is larger than the sum of its proper divisors (137830409).

1218534391 is a wasteful number, since it uses less digits than its factorization.

1218534391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50550.

The product of its digits is 25920, while the sum is 37.

The square root of 1218534391 is about 34907.5119565975. The cubic root of 1218534391 is about 1068.1016770573.

The spelling of 1218534391 in words is "one billion, two hundred eighteen million, five hundred thirty-four thousand, three hundred ninety-one".