1639918431649 has 9 divisors (see below), whose sum is σ = 1742081806297. Its totient is φ = 1543432152064.

The previous prime is 1639918431647. The next prime is 1639918431659. The reversal of 1639918431649 is 9461348199361.

The square root of 1639918431649 is 1280593.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 43658013025 + 1596260418624 = 208945^2 + 1263432^2 .

It is not a de Polignac number, because 1639918431649 - 2¹ = 1639918431647 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1639918431647) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 21732417 + ... + 21807745.

Almost surely, 2^{1639918431649} is an apocalyptic number.

1639918431649 is the 1280593-rd square number.

1639918431649 is the 640297-th centered octagonal number.

It is an amenable number.

1639918431649 is a deficient number, since it is larger than the sum of its proper divisors (102163374648).

1639918431649 is an frugal number, since it uses more digits than its factorization.

1639918431649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150692 (or 75346 counting only the distinct ones).

The product of its digits is 30233088, while the sum is 64.

Multiplying 1639918431649 by its sum of digits (64), we get a square (104954779625536 = 10244744²).

The spelling of 1639918431649 in words is "one trillion, six hundred thirty-nine billion, nine hundred eighteen million, four hundred thirty-one thousand, six hundred forty-nine".