1778640993649 has 27 divisors (see below), whose sum is σ = 1940453498307. Its totient is φ = 1629579484416.

The previous prime is 1778640993637. The next prime is 1778640993709. The reversal of 1778640993649 is 9463990468771.

The square root of 1778640993649 is 1333657.

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

It can be written as a sum of positive squares in 13 ways, for example, as 534149031025 + 1244491962624 = 730855^2 + 1115568^2 .

It is a de Polignac number, because none of the positive numbers 2^k-1778640993649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1778640993049) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 2999394297 + ... + 2999394889.

Almost surely, 2^{1778640993649} is an apocalyptic number.

1778640993649 is the 1333657-th square number.

1778640993649 is the 666829-th centered octagonal number.

It is an amenable number.

1778640993649 is a deficient number, since it is larger than the sum of its proper divisors (161812504658).

1778640993649 is an frugal number, since it uses more digits than its factorization.

1778640993649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1558 (or 779 counting only the distinct ones).

The product of its (nonzero) digits is 493807104, while the sum is 73.

The spelling of 1778640993649 in words is "one trillion, seven hundred seventy-eight billion, six hundred forty million, nine hundred ninety-three thousand, six hundred forty-nine".