261691560 has 384 divisors, whose sum is σ = 1009008000. Its totient is φ = 60466176.

The previous prime is 261691559. The next prime is 261691589. The reversal of 261691560 is 65196162.

261691560 is a `hidden beast` number, since 2 + 6 + 1 + 6 + 91 + 560 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2400786 + ... + 2400894.

It is an arithmetic number, because the mean of its divisors is an integer number (2627625).

Almost surely, 2^261691560 is an apocalyptic number.

261691560 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 261691560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (504504000).

261691560 is an abundant number, since it is smaller than the sum of its proper divisors (747316440).

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

261691560 is a wasteful number, since it uses less digits than its factorization.

261691560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167 (or 151 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 261691560 is about 16176.8835070294. The cubic root of 261691560 is about 639.6315913559.

The spelling of 261691560 in words is "two hundred sixty-one million, six hundred ninety-one thousand, five hundred sixty".