1231605 has 20 divisors (see below), whose sum is σ = 2208492. Its totient is φ = 656640.

The previous prime is 1231597. The next prime is 1231613. The reversal of 1231605 is 5061321.

It is an interprime number because it is at equal distance from previous prime (1231597) and next prime (1231613).

It can be written as a sum of positive squares in 2 ways, for example, as 910116 + 321489 = 954^2 + 567^2 .

It is not a de Polignac number, because 1231605 - 2³ = 1231597 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1116 + ... + 1925.

2^1231605 is an apocalyptic number.

1231605 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1231605 is a deficient number, since it is larger than the sum of its proper divisors (976887).

1231605 is an equidigital number, since it uses as much as digits as its factorization.

1231605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3058 (or 3049 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 1231605 is about 1109.7770046275. Note that the first 3 decimals coincide. The cubic root of 1231605 is about 107.1907100530.

Adding to 1231605 its reverse (5061321), we get a palindrome (6292926).

It can be divided in two parts, 123 and 1605, that added together give a cube (1728 = 12³).

The spelling of 1231605 in words is "one million, two hundred thirty-one thousand, six hundred five".