6378515681 has 2 divisors, whose sum is σ = 6378515682. Its totient is φ = 6378515680.

The previous prime is 6378515657. The next prime is 6378515743. The reversal of 6378515681 is 1865158736.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4638291025 + 1740224656 = 68105^2 + 41716^2 .

It is a cyclic number.

It is not a de Polignac number, because 6378515681 - 2¹⁸ = 6378253537 is a prime.

It is a super-2 number, since 2×6378515681² = 81370924585525787522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (6378515881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3189257840 + 3189257841.

It is an arithmetic number, because the mean of its divisors is an integer number (3189257841).

Almost surely, 2^6378515681 is an apocalyptic number.

It is an amenable number.

6378515681 is a deficient number, since it is larger than the sum of its proper divisors (1).

6378515681 is an equidigital number, since it uses as much as digits as its factorization.

6378515681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1209600, while the sum is 50.

The square root of 6378515681 is about 79865.6101272632. The cubic root of 6378515681 is about 1854.5556757481. Note that the first 3 decimals are identical.

The spelling of 6378515681 in words is "six billion, three hundred seventy-eight million, five hundred fifteen thousand, six hundred eighty-one".