2561965728 has 96 divisors (see below), whose sum is σ = 7831022976. Its totient is φ = 718169088.

The previous prime is 2561965727. The next prime is 2561965741. The reversal of 2561965728 is 8275691652.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (2561965727) 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, 351 + ... + 71582.

It is an arithmetic number, because the mean of its divisors is an integer number (81573156).

Almost surely, 2^2561965728 is an apocalyptic number.

2561965728 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 2561965728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3915511488).

2561965728 is an abundant number, since it is smaller than the sum of its proper divisors (5269057248).

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

2561965728 is a wasteful number, since it uses less digits than its factorization.

2561965728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72006 (or 71998 counting only the distinct ones).

The product of its digits is 1814400, while the sum is 51.

The square root of 2561965728 is about 50615.8643905248. The cubic root of 2561965728 is about 1368.3308081344.

The spelling of 2561965728 in words is "two billion, five hundred sixty-one million, nine hundred sixty-five thousand, seven hundred twenty-eight".