1218139217 has 4 divisors (see below), whose sum is σ = 1246468080. Its totient is φ = 1189810356.

The previous prime is 1218139207. The next prime is 1218139259. The reversal of 1218139217 is 7129318121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7129318121 = 61403 ⋅116107.

It is a cyclic number.

It is not a de Polignac number, because 1218139217 - 2¹⁰ = 1218138193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1218139207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14164367 + ... + 14164452.

It is an arithmetic number, because the mean of its divisors is an integer number (311617020).

Almost surely, 2^1218139217 is an apocalyptic number.

It is an amenable number.

1218139217 is a deficient number, since it is larger than the sum of its proper divisors (28328863).

1218139217 is an equidigital number, since it uses as much as digits as its factorization.

1218139217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28328862.

The product of its digits is 6048, while the sum is 35.

The square root of 1218139217 is about 34901.8511973219. The cubic root of 1218139217 is about 1067.9862018188.

The spelling of 1218139217 in words is "one billion, two hundred eighteen million, one hundred thirty-nine thousand, two hundred seventeen".