1968646781 has 4 divisors (see below), whose sum is σ = 1969283100. Its totient is φ = 1968010464.

The previous prime is 1968646739. The next prime is 1968646793. The reversal of 1968646781 is 1876468691.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1876468691 = 461 ⋅4070431.

It can be written as a sum of positive squares in 2 ways, for example, as 587335225 + 1381311556 = 24235^2 + 37166^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1968646781 is a prime.

It is a super-2 number, since 2×1968646781² = 7751140296683323922, 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 (1968646721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 313496 + ... + 319713.

It is an arithmetic number, because the mean of its divisors is an integer number (492320775).

Almost surely, 2^1968646781 is an apocalyptic number.

It is an amenable number.

1968646781 is a deficient number, since it is larger than the sum of its proper divisors (636319).

1968646781 is an equidigital number, since it uses as much as digits as its factorization.

1968646781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 636318.

The product of its digits is 3483648, while the sum is 56.

The square root of 1968646781 is about 44369.4352116409. The cubic root of 1968646781 is about 1253.3025799679.

The spelling of 1968646781 in words is "one billion, nine hundred sixty-eight million, six hundred forty-six thousand, seven hundred eighty-one".