261644328960 has 896 divisors, whose sum is σ = 1049728273920. Its totient is φ = 54257516544.

The previous prime is 261644328941. The next prime is 261644328973. The reversal of 261644328960 is 69823446162.

It is a tau number, because it is divible by the number of its divisors (896).

It is a Harshad number since it is a multiple of its sum of digits (51).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 424058572 + ... + 424059188.

Almost surely, 2^261644328960 is an apocalyptic number.

261644328960 is a gapful number since it is divisible by the number (20) 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 261644328960, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (524864136960).

261644328960 is an abundant number, since it is smaller than the sum of its proper divisors (788083944960).

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

261644328960 is a wasteful number, since it uses less digits than its factorization.

261644328960 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 704 (or 680 counting only the distinct ones).

The product of its (nonzero) digits is 2985984, while the sum is 51.

The spelling of 261644328960 in words is "two hundred sixty-one billion, six hundred forty-four million, three hundred twenty-eight thousand, nine hundred sixty".