1205261821 has 2 divisors, whose sum is σ = 1205261822. Its totient is φ = 1205261820.

The previous prime is 1205261773. The next prime is 1205261831. The reversal of 1205261821 is 1281625021.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 852348025 + 352913796 = 29195^2 + 18786^2 .

It is a cyclic number.

It is not a de Polignac number, because 1205261821 - 2¹¹ = 1205259773 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1205261821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1205261831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 602630910 + 602630911.

It is an arithmetic number, because the mean of its divisors is an integer number (602630911).

Almost surely, 2^1205261821 is an apocalyptic number.

It is an amenable number.

1205261821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1205261821 is an equidigital number, since it uses as much as digits as its factorization.

1205261821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 1205261821 is about 34716.8809226866. The cubic root of 1205261821 is about 1064.2095042845.

Adding to 1205261821 its reverse (1281625021), we get a palindrome (2486886842).

The spelling of 1205261821 in words is "one billion, two hundred five million, two hundred sixty-one thousand, eight hundred twenty-one".