1218829981 has 4 divisors (see below), whose sum is σ = 1220024764. Its totient is φ = 1217635200.

The previous prime is 1218829967. The next prime is 1218829999. The reversal of 1218829981 is 1899288121.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1899288121 = 557 ⋅3409853.

It can be written as a sum of positive squares in 2 ways, for example, as 856498756 + 362331225 = 29266^2 + 19035^2 .

It is a cyclic number.

It is not a de Polignac number, because 1218829981 - 2⁷ = 1218829853 is a prime.

It is a super-2 number, since 2×1218829981² = 2971093045168920722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1218829921) 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 3 ways as a sum of consecutive naturals, for example, 595860 + ... + 597901.

It is an arithmetic number, because the mean of its divisors is an integer number (305006191).

Almost surely, 2^1218829981 is an apocalyptic number.

It is an amenable number.

1218829981 is a deficient number, since it is larger than the sum of its proper divisors (1194783).

1218829981 is a wasteful number, since it uses less digits than its factorization.

1218829981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1194782.

The product of its digits is 165888, while the sum is 49.

The square root of 1218829981 is about 34911.7456023041. The cubic root of 1218829981 is about 1068.1880361707.

The spelling of 1218829981 in words is "one billion, two hundred eighteen million, eight hundred twenty-nine thousand, nine hundred eighty-one".