261811760 has 80 divisors (see below), whose sum is σ = 725953536. Its totient is φ = 85857024.

The previous prime is 261811757. The next prime is 261811793. The reversal of 261811760 is 67118162.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2717 + ... + 23043.

Almost surely, 2^261811760 is an apocalyptic number.

261811760 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 261811760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (362976768).

261811760 is an abundant number, since it is smaller than the sum of its proper divisors (464141776).

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

261811760 is a wasteful number, since it uses less digits than its factorization.

261811760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20370 (or 20364 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 261811760 is about 16180.5982584081. The cubic root of 261811760 is about 639.7295080903.

The spelling of 261811760 in words is "two hundred sixty-one million, eight hundred eleven thousand, seven hundred sixty".