261506 has 8 divisors (see below), whose sum is σ = 448320. Its totient is φ = 112068.

The previous prime is 261467. The next prime is 261509. The reversal of 261506 is 605162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (261509) by changing a digit.

261506 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 3 ways as a sum of consecutive naturals, for example, 9326 + ... + 9353.

It is an arithmetic number, because the mean of its divisors is an integer number (56040).

2²⁶¹⁵⁰⁶ is an apocalyptic number.

261506 is a deficient number, since it is larger than the sum of its proper divisors (186814).

261506 is a wasteful number, since it uses less digits than its factorization.

261506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18688.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 261506 is about 511.3765735737. The cubic root of 261506 is about 63.9480372490.

Adding to 261506 its reverse (605162), we get a palindrome (866668).

It can be divided in two parts, 261 and 506, that added together give a palindrome (767).

The spelling of 261506 in words is "two hundred sixty-one thousand, five hundred six".