261891960 has 128 divisors (see below), whose sum is σ = 862272000. Its totient is φ = 63106560.

The previous prime is 261891941. The next prime is 261891967. The reversal of 261891960 is 69198162.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261891967) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 262182 + ... + 263178.

It is an arithmetic number, because the mean of its divisors is an integer number (6736500).

Almost surely, 2^261891960 is an apocalyptic number.

261891960 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 261891960, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (431136000).

261891960 is an abundant number, since it is smaller than the sum of its proper divisors (600380040).

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

261891960 is a wasteful number, since it uses less digits than its factorization.

261891960 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1221 (or 1217 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 42.

The square root of 261891960 is about 16183.0763453677. The cubic root of 261891960 is about 639.7948235528.

The spelling of 261891960 in words is "two hundred sixty-one million, eight hundred ninety-one thousand, nine hundred sixty".