661265 has 12 divisors (see below), whose sum is σ = 873012. Its totient is φ = 480480.

The previous prime is 661259. The next prime is 661267. The reversal of 661265 is 562166.

It can be written as a sum of positive squares in 2 ways, for example, as 495616 + 165649 = 704^2 + 407^2 .

It is not a de Polignac number, because 661265 - 2⁶ = 661201 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661267) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59 + ... + 1151.

It is an arithmetic number, because the mean of its divisors is an integer number (72751).

2⁶⁶¹²⁶⁵ is an apocalyptic number.

It is an amenable number.

661265 is a deficient number, since it is larger than the sum of its proper divisors (211747).

661265 is a wasteful number, since it uses less digits than its factorization.

661265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1120 (or 1109 counting only the distinct ones).

The product of its digits is 2160, while the sum is 26.

The square root of 661265 is about 813.1820214442. The cubic root of 661265 is about 87.1214668324.

Subtracting from 661265 its reverse (562166), we obtain a palindrome (99099).

It can be divided in two parts, 66 and 1265, that added together give a palindrome (1331).

The spelling of 661265 in words is "six hundred sixty-one thousand, two hundred sixty-five".