261623 has 4 divisors (see below), whose sum is σ = 262680. Its totient is φ = 260568.

The previous prime is 261619. The next prime is 261631. The reversal of 261623 is 326162.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 261623 - 2² = 261619 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 261595 and 261604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68 + ... + 726.

It is an arithmetic number, because the mean of its divisors is an integer number (65670).

2²⁶¹⁶²³ is an apocalyptic number.

261623 is a deficient number, since it is larger than the sum of its proper divisors (1057).

261623 is an equidigital number, since it uses as much as digits as its factorization.

261623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1056.

The product of its digits is 432, while the sum is 20.

The square root of 261623 is about 511.4909578868. The cubic root of 261623 is about 63.9575727916.

Adding to 261623 its reverse (326162), we get a palindrome (587785).

The spelling of 261623 in words is "two hundred sixty-one thousand, six hundred twenty-three".