2561778768 has 80 divisors (see below), whose sum is σ = 6898556480. Its totient is φ = 818408448.

The previous prime is 2561778767. The next prime is 2561778809. The reversal of 2561778768 is 8678771652.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2561778767) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 108228 + ... + 129756.

It is an arithmetic number, because the mean of its divisors is an integer number (86231956).

Almost surely, 2^2561778768 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 2561778768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3449278240).

2561778768 is an abundant number, since it is smaller than the sum of its proper divisors (4336777712).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

2561778768 is a wasteful number, since it uses less digits than its factorization.

2561778768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21644 (or 21638 counting only the distinct ones).

The product of its digits is 7902720, while the sum is 57.

The square root of 2561778768 is about 50614.0175050351. The cubic root of 2561778768 is about 1368.2975225798.

The spelling of 2561778768 in words is "two billion, five hundred sixty-one million, seven hundred seventy-eight thousand, seven hundred sixty-eight".