20128260267781 has 4 divisors (see below), whose sum is σ = 20130693282252. Its totient is φ = 20125827253312.

The previous prime is 20128260267727. The next prime is 20128260267803. The reversal of 20128260267781 is 18776206282102.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15883939237156 + 4244321030625 = 3985466^2 + 2060175^2 .

It is a cyclic number.

It is not a de Polignac number, because 20128260267781 - 2⁷ = 20128260267653 is a prime.

It is a super-2 number, since 2×20128260267781² (a number of 27 digits) 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 (20128260367781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1216494826 + ... + 1216511371.

It is an arithmetic number, because the mean of its divisors is an integer number (5032673320563).

Almost surely, 2^{20128260267781} is an apocalyptic number.

It is an amenable number.

20128260267781 is a deficient number, since it is larger than the sum of its proper divisors (2433014471).

20128260267781 is an equidigital number, since it uses as much as digits as its factorization.

20128260267781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2433014470.

The product of its (nonzero) digits is 1806336, while the sum is 52.

The spelling of 20128260267781 in words is "twenty trillion, one hundred twenty-eight billion, two hundred sixty million, two hundred sixty-seven thousand, seven hundred eighty-one".