1218981509 has 2 divisors, whose sum is σ = 1218981510. Its totient is φ = 1218981508.

The previous prime is 1218981497. The next prime is 1218981523. The reversal of 1218981509 is 9051898121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 863772100 + 355209409 = 29390^2 + 18847^2 .

It is a cyclic number.

It is not a de Polignac number, because 1218981509 - 2⁴ = 1218981493 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1218981509.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1218981529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 609490754 + 609490755.

It is an arithmetic number, because the mean of its divisors is an integer number (609490755).

Almost surely, 2^1218981509 is an apocalyptic number.

It is an amenable number.

1218981509 is a deficient number, since it is larger than the sum of its proper divisors (1).

1218981509 is an equidigital number, since it uses as much as digits as its factorization.

1218981509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 51840, while the sum is 44.

The square root of 1218981509 is about 34913.9156927435. The cubic root of 1218981509 is about 1068.2323009416.

The spelling of 1218981509 in words is "one billion, two hundred eighteen million, nine hundred eighty-one thousand, five hundred nine".