27728776781 has 4 divisors (see below), whose sum is σ = 27729282012. Its totient is φ = 27728271552.

The previous prime is 27728776703. The next prime is 27728776849. The reversal of 27728776781 is 18767782772.

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 19518604681 + 8210172100 = 139709^2 + 90610^2 .

It is a cyclic number.

It is not a de Polignac number, because 27728776781 - 2²² = 27724582477 is a prime.

It is a super-2 number, since 2×27728776781² (a number of 22 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 (27728773781) 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, 158636 + ... + 283941.

It is an arithmetic number, because the mean of its divisors is an integer number (6932320503).

Almost surely, 2^27728776781 is an apocalyptic number.

It is an amenable number.

27728776781 is a deficient number, since it is larger than the sum of its proper divisors (505231).

27728776781 is an equidigital number, since it uses as much as digits as its factorization.

27728776781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 505230.

The product of its digits is 25815552, while the sum is 62.

The spelling of 27728776781 in words is "twenty-seven billion, seven hundred twenty-eight million, seven hundred seventy-six thousand, seven hundred eighty-one".