2778557661 has 80 divisors (see below), whose sum is σ = 4707616320. Its totient is φ = 1618341120.

The previous prime is 2778557647. The next prime is 2778557669. The reversal of 2778557661 is 1667558772.

It is a happy number.

2778557661 is a `hidden beast` number, since 2 + 7 + 7 + 8 + 5 + 576 + 61 = 666.

It is not a de Polignac number, because 2778557661 - 2⁷ = 2778557533 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 2778557598 and 2778557607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2778557669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 2933590 + ... + 2934536.

It is an arithmetic number, because the mean of its divisors is an integer number (58845204).

Almost surely, 2^2778557661 is an apocalyptic number.

It is an amenable number.

2778557661 is a deficient number, since it is larger than the sum of its proper divisors (1929058659).

2778557661 is a wasteful number, since it uses less digits than its factorization.

2778557661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1096 (or 1087 counting only the distinct ones).

The product of its digits is 4939200, while the sum is 54.

The square root of 2778557661 is about 52712.0257721139. The cubic root of 2778557661 is about 1405.8526523233.

The spelling of 2778557661 in words is "two billion, seven hundred seventy-eight million, five hundred fifty-seven thousand, six hundred sixty-one".