261440643576544 has 144 divisors (see below), whose sum is σ = 543497247991152. Its totient is φ = 123780213438464.

The previous prime is 261440643576451. The next prime is 261440643576547. The reversal of 261440643576544 is 445675346044162.

It is a happy number.

261440643576544 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×261440643576544² (a number of 30 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261440643576547) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 682159179 + ... + 682542325.

It is an arithmetic number, because the mean of its divisors is an integer number (3774286444383).

Almost surely, 2^{261440643576544} 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 261440643576544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (271748623995576).

261440643576544 is an abundant number, since it is smaller than the sum of its proper divisors (282056604414608).

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

261440643576544 is a wasteful number, since it uses less digits than its factorization.

261440643576544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 383609 (or 383578 counting only the distinct ones).

The product of its (nonzero) digits is 232243200, while the sum is 61.

The spelling of 261440643576544 in words is "two hundred sixty-one trillion, four hundred forty billion, six hundred forty-three million, five hundred seventy-six thousand, five hundred forty-four".