27780856781 has 4 divisors (see below), whose sum is σ = 27980719200. Its totient is φ = 27580994364.

The previous prime is 27780856757. The next prime is 27780856787. The reversal of 27780856781 is 18765808772.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 27780856781 - 2⁶ = 27780856717 is a prime.

It is a super-2 number, since 2×27780856781² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 27780856781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27780856787) 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, 99931001 + ... + 99931278.

It is an arithmetic number, because the mean of its divisors is an integer number (6995179800).

Almost surely, 2^27780856781 is an apocalyptic number.

It is an amenable number.

27780856781 is a deficient number, since it is larger than the sum of its proper divisors (199862419).

27780856781 is a wasteful number, since it uses less digits than its factorization.

27780856781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199862418.

The product of its (nonzero) digits is 10536960, while the sum is 59.

The spelling of 27780856781 in words is "twenty-seven billion, seven hundred eighty million, eight hundred fifty-six thousand, seven hundred eighty-one".