1218025781 has 12 divisors (see below), whose sum is σ = 1465747020. Its totient is φ = 1008020160.

The previous prime is 1218025771. The next prime is 1218025793. The reversal of 1218025781 is 1875208121.

It can be written as a sum of positive squares in 2 ways, for example, as 208947025 + 1009078756 = 14455^2 + 31766^2 .

It is not a de Polignac number, because 1218025781 - 2¹⁰ = 1218024757 is a prime.

It is a super-2 number, since 2×1218025781² = 2967173606361319922, 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 (1218025771) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 427160 + ... + 430001.

It is an arithmetic number, because the mean of its divisors is an integer number (122145585).

Almost surely, 2^1218025781 is an apocalyptic number.

It is an amenable number.

1218025781 is a deficient number, since it is larger than the sum of its proper divisors (247721239).

1218025781 is an equidigital number, since it uses as much as digits as its factorization.

1218025781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 857204 (or 857197 counting only the distinct ones).

The product of its (nonzero) digits is 8960, while the sum is 35.

The square root of 1218025781 is about 34900.2260880929. The cubic root of 1218025781 is about 1067.9530496574.

The spelling of 1218025781 in words is "one billion, two hundred eighteen million, twenty-five thousand, seven hundred eighty-one".