261668772540 has 384 divisors, whose sum is σ = 980430796800. Its totient is φ = 56599326720.

The previous prime is 261668772539. The next prime is 261668772551. The reversal of 261668772540 is 45277866162.

It is a happy number.

261668772540 is a `hidden beast` number, since 2 + 6 + 16 + 6 + 87 + 7 + 2 + 540 = 666.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 97745682 + ... + 97748358.

It is an arithmetic number, because the mean of its divisors is an integer number (2553205200).

Almost surely, 2^261668772540 is an apocalyptic number.

261668772540 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 261668772540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (490215398400).

261668772540 is an abundant number, since it is smaller than the sum of its proper divisors (718762024260).

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

261668772540 is a wasteful number, since it uses less digits than its factorization.

261668772540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4082 (or 4074 counting only the distinct ones).

The product of its (nonzero) digits is 6773760, while the sum is 54.

The spelling of 261668772540 in words is "two hundred sixty-one billion, six hundred sixty-eight million, seven hundred seventy-two thousand, five hundred forty".