6440778893 has 2 divisors, whose sum is σ = 6440778894. Its totient is φ = 6440778892.

The previous prime is 6440778889. The next prime is 6440778907. The reversal of 6440778893 is 3988770446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5705989444 + 734789449 = 75538^2 + 27107^2 .

It is a cyclic number.

It is not a de Polignac number, because 6440778893 - 2² = 6440778889 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6440778853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3220389446 + 3220389447.

It is an arithmetic number, because the mean of its divisors is an integer number (3220389447).

Almost surely, 2^6440778893 is an apocalyptic number.

It is an amenable number.

6440778893 is a deficient number, since it is larger than the sum of its proper divisors (1).

6440778893 is an equidigital number, since it uses as much as digits as its factorization.

6440778893 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8128512, while the sum is 56.

The square root of 6440778893 is about 80254.4633836648. The cubic root of 6440778893 is about 1860.5704972355.

The spelling of 6440778893 in words is "six billion, four hundred forty million, seven hundred seventy-eight thousand, eight hundred ninety-three".