261520 has 40 divisors (see below), whose sum is σ = 696384. Its totient is φ = 89472.

The previous prime is 261509. The next prime is 261523. The reversal of 261520 is 25162.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a nialpdrome in base 8.

It is a junction number, because it is equal to n+sod(n) for n = 261494 and 261503.

It is not an unprimeable number, because it can be changed into a prime (261523) by changing a digit.

261520 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 327 + ... + 793.

2²⁶¹⁵²⁰ is an apocalyptic number.

261520 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 261520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (348192).

261520 is an abundant number, since it is smaller than the sum of its proper divisors (434864).

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

261520 is a wasteful number, since it uses less digits than its factorization.

261520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 487 (or 481 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 261520 is about 511.3902619331. The cubic root of 261520 is about 63.9491784039.

Adding to 261520 its reverse (25162), we get a palindrome (286682).

The spelling of 261520 in words is "two hundred sixty-one thousand, five hundred twenty".