1261665 has 36 divisors (see below), whose sum is σ = 2329236. Its totient is φ = 631488.

The previous prime is 1261649. The next prime is 1261697. The reversal of 1261665 is 5661621.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 685584 + 576081 = 828^2 + 759^2 .

It is not a de Polignac number, because 1261665 - 2⁴ = 1261649 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 23779 + ... + 23831.

It is an arithmetic number, because the mean of its divisors is an integer number (64701).

2^1261665 is an apocalyptic number.

1261665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1261665 is a deficient number, since it is larger than the sum of its proper divisors (1067571).

1261665 is a wasteful number, since it uses less digits than its factorization.

1261665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110 (or 84 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 1261665 is about 1123.2386211309. The cubic root of 1261665 is about 108.0557839388.

The spelling of 1261665 in words is "one million, two hundred sixty-one thousand, six hundred sixty-five".