1638739189561 has 2 divisors, whose sum is σ = 1638739189562. Its totient is φ = 1638739189560.

The previous prime is 1638739189523. The next prime is 1638739189601. The reversal of 1638739189561 is 1659819378361.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1181012521536 + 457726668025 = 1086744^2 + 676555^2 .

It is a cyclic number.

It is not a de Polignac number, because 1638739189561 - 2⁹ = 1638739189049 is a prime.

It is a super-2 number, since 2×1638739189561² (a number of 25 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1638739189511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 819369594780 + 819369594781.

It is an arithmetic number, because the mean of its divisors is an integer number (819369594781).

Almost surely, 2^{1638739189561} is an apocalyptic number.

It is an amenable number.

1638739189561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1638739189561 is an equidigital number, since it uses as much as digits as its factorization.

1638739189561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 58786560, while the sum is 67.

The spelling of 1638739189561 in words is "one trillion, six hundred thirty-eight billion, seven hundred thirty-nine million, one hundred eighty-nine thousand, five hundred sixty-one".