261720 has 48 divisors (see below), whose sum is σ = 851760. Its totient is φ = 69696.

The previous prime is 261713. The next prime is 261721. The reversal of 261720 is 27162.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 261693 and 261702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261721) by changing a digit.

261720 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4 + ... + 723.

It is an arithmetic number, because the mean of its divisors is an integer number (17745).

2²⁶¹⁷²⁰ is an apocalyptic number.

261720 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 261720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (425880).

261720 is an abundant number, since it is smaller than the sum of its proper divisors (590040).

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

261720 is a wasteful number, since it uses less digits than its factorization.

261720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 744 (or 737 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 261720 is about 511.5857699350. The cubic root of 261720 is about 63.9654761717.

Adding to 261720 its reverse (27162), we get a palindrome (288882).

The spelling of 261720 in words is "two hundred sixty-one thousand, seven hundred twenty".