261435870864 has 225 divisors, whose sum is σ = 880643451897. Its totient is φ = 74659148928.

The previous prime is 261435870853. The next prime is 261435870877. The reversal of 261435870864 is 468078534162.

It is a happy number.

The square root of 261435870864 is 511308.

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

261435870864 is a `hidden beast` number, since 2 + 61 + 435 + 8 + 70 + 86 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 259378341264 + 2057529600 = 509292^2 + 45360^2 .

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a self number, because there is not a number n which added to its sum of digits gives 261435870864.

It is an unprimeable number.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 128848602 + ... + 128850630.

Almost surely, 2^261435870864 is an apocalyptic number.

261435870864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

261435870864 is the 511308-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261435870864

261435870864 is an abundant number, since it is smaller than the sum of its proper divisors (619207581033).

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

261435870864 is an frugal number, since it uses more digits than its factorization.

261435870864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4092 (or 2041 counting only the distinct ones).

The product of its (nonzero) digits is 7741440, while the sum is 54.

The spelling of 261435870864 in words is "two hundred sixty-one billion, four hundred thirty-five million, eight hundred seventy thousand, eight hundred sixty-four".