261384742564 has 81 divisors (see below), whose sum is σ = 534494081569. Its totient is φ = 111740548480.

The previous prime is 261384742561. The next prime is 261384742579. The reversal of 261384742564 is 465247483162.

The square root of 261384742564 is 511258.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 203500232100 + 57884510464 = 451110^2 + 240592^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261384742561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 191209809 + ... + 191211175.

Almost surely, 2^261384742564 is an apocalyptic number.

261384742564 is the 511258-th square number.

It is an amenable number.

261384742564 is an abundant number, since it is smaller than the sum of its proper divisors (273109339005).

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

261384742564 is a wasteful number, since it uses less digits than its factorization.

261384742564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2794 (or 1397 counting only the distinct ones).

The product of its digits is 7741440, while the sum is 52.

The spelling of 261384742564 in words is "two hundred sixty-one billion, three hundred eighty-four million, seven hundred forty-two thousand, five hundred sixty-four".