2778356781 has 14 divisors (see below), whose sum is σ = 4165630670. Its totient is φ = 1852237368.

The previous prime is 2778356761. The next prime is 2778356821. The reversal of 2778356781 is 1876538772.

2778356781 is a `hidden beast` number, since 2 + 7 + 78 + 3 + 567 + 8 + 1 = 666.

2778356781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 2276148681 + 502208100 = 47709^2 + 22410^2 .

It is not a de Polignac number, because 2778356781 - 2⁷ = 2778356653 is a prime.

It is a super-2 number, since 2×2778356781² = 15438532805057363922, which 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 (2778356701) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 1904866 + ... + 1906323.

Almost surely, 2^2778356781 is an apocalyptic number.

It is an amenable number.

2778356781 is a deficient number, since it is larger than the sum of its proper divisors (1387273889).

2778356781 is an frugal number, since it uses more digits than its factorization.

2778356781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3811207 (or 3811192 counting only the distinct ones).

The product of its digits is 3951360, while the sum is 54.

The square root of 2778356781 is about 52710.1202901302. The cubic root of 2778356781 is about 1405.8187720971.

The spelling of 2778356781 in words is "two billion, seven hundred seventy-eight million, three hundred fifty-six thousand, seven hundred eighty-one".