1638618361 has 2 divisors, whose sum is σ = 1638618362. Its totient is φ = 1638618360.

The previous prime is 1638618343. The next prime is 1638618403. The reversal of 1638618361 is 1638168361.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1388978361 + 249640000 = 37269^2 + 15800^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1638618361 is a prime.

It is not a weakly prime, because it can be changed into another prime (1638618161) 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 as a sum of consecutive naturals, namely, 819309180 + 819309181.

It is an arithmetic number, because the mean of its divisors is an integer number (819309181).

Almost surely, 2^1638618361 is an apocalyptic number.

It is an amenable number.

1638618361 is a deficient number, since it is larger than the sum of its proper divisors (1).

1638618361 is an equidigital number, since it uses as much as digits as its factorization.

1638618361 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 124416, while the sum is 43.

The square root of 1638618361 is about 40479.8512966636. The cubic root of 1638618361 is about 1178.9424502073.

The spelling of 1638618361 in words is "one billion, six hundred thirty-eight million, six hundred eighteen thousand, three hundred sixty-one".