2561221782720 has 84 divisors (see below), whose sum is σ = 8809535766720. Its totient is φ = 682992474624.

The previous prime is 2561221782649. The next prime is 2561221782727. The reversal of 2561221782720 is 272871221652.

2561221782720 is a `hidden beast` number, since 2 + 5 + 612 + 2 + 1 + 7 + 8 + 2 + 7 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (2561221782727) 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 11 ways as a sum of consecutive naturals, for example, 444653680 + ... + 444659439.

Almost surely, 2^{2561221782720} is an apocalyptic number.

2561221782720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

2561221782720 is an abundant number, since it is smaller than the sum of its proper divisors (6248313984000).

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

2561221782720 is a wasteful number, since it uses less digits than its factorization.

2561221782720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 889313142 (or 889313129 counting only the distinct ones).

The product of its (nonzero) digits is 376320, while the sum is 45.

The spelling of 2561221782720 in words is "two trillion, five hundred sixty-one billion, two hundred twenty-one million, seven hundred eighty-two thousand, seven hundred twenty".