2566720781 has 2 divisors, whose sum is σ = 2566720782. Its totient is φ = 2566720780.

The previous prime is 2566720769. The next prime is 2566720799. The reversal of 2566720781 is 1870276652.

2566720781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2016818281 + 549902500 = 44909^2 + 23450^2 .

It is a cyclic number.

It is not a de Polignac number, because 2566720781 - 2¹⁸ = 2566458637 is a prime.

It is a super-2 number, since 2×2566720781² = 13176111135234499922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2566720711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1283360390 + 1283360391.

It is an arithmetic number, because the mean of its divisors is an integer number (1283360391).

Almost surely, 2^2566720781 is an apocalyptic number.

It is an amenable number.

2566720781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2566720781 is an equidigital number, since it uses as much as digits as its factorization.

2566720781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 282240, while the sum is 44.

The square root of 2566720781 is about 50662.8145783473. The cubic root of 2566720781 is about 1369.1768335392.

The spelling of 2566720781 in words is "two billion, five hundred sixty-six million, seven hundred twenty thousand, seven hundred eighty-one".