261431265021771 has 72 divisors (see below), whose sum is σ = 417785821061616. Its totient is φ = 144833844080640.

The previous prime is 261431265021769. The next prime is 261431265021781. The reversal of 261431265021771 is 177120562134162.

It is a happy number.

It is not a de Polignac number, because 261431265021771 - 2¹ = 261431265021769 is a prime.

It is a super-2 number, since 2×261431265021771² (a number of 30 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 261431265021771.

It is not an unprimeable number, because it can be changed into a prime (261431265021781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 24109710 + ... + 33228611.

It is an arithmetic number, because the mean of its divisors is an integer number (5802580848078).

Almost surely, 2^{261431265021771} is an apocalyptic number.

261431265021771 is a deficient number, since it is larger than the sum of its proper divisors (156354556039845).

261431265021771 is a wasteful number, since it uses less digits than its factorization.

261431265021771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57338413 (or 57338377 counting only the distinct ones).

The product of its (nonzero) digits is 846720, while the sum is 48.

The spelling of 261431265021771 in words is "two hundred sixty-one trillion, four hundred thirty-one billion, two hundred sixty-five million, twenty-one thousand, seven hundred seventy-one".