1205643861 has 6 divisors (see below), whose sum is σ = 1741485590. Its totient is φ = 803762568.

The previous prime is 1205643851. The next prime is 1205643869. The reversal of 1205643861 is 1683465021.

It is a happy number.

1205643861 is a `hidden beast` number, since 1 + 2 + 0 + 5 + 643 + 8 + 6 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 837234225 + 368409636 = 28935^2 + 19194^2 .

It is not a de Polignac number, because 1205643861 - 2¹⁴ = 1205627477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1205643869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 66980206 + ... + 66980223.

Almost surely, 2^1205643861 is an apocalyptic number.

It is an amenable number.

1205643861 is a deficient number, since it is larger than the sum of its proper divisors (535841729).

1205643861 is a wasteful number, since it uses less digits than its factorization.

1205643861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133960435 (or 133960432 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The square root of 1205643861 is about 34722.3827091402. The cubic root of 1205643861 is about 1064.3219356367.

The spelling of 1205643861 in words is "one billion, two hundred five million, six hundred forty-three thousand, eight hundred sixty-one".