1205312921 has 2 divisors, whose sum is σ = 1205312922. Its totient is φ = 1205312920.

The previous prime is 1205312897. The next prime is 1205312923. The reversal of 1205312921 is 1292135021.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1133062921 + 72250000 = 33661^2 + 8500^2 .

It is an emirp because it is prime and its reverse (1292135021) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1205312921 - 2¹⁰ = 1205311897 is a prime.

It is a Sophie Germain prime.

Together with 1205312923, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1205312923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 602656460 + 602656461.

It is an arithmetic number, because the mean of its divisors is an integer number (602656461).

Almost surely, 2^1205312921 is an apocalyptic number.

It is an amenable number.

1205312921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1205312921 is an equidigital number, since it uses as much as digits as its factorization.

1205312921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 1205312921 is about 34717.6168680974. The cubic root of 1205312921 is about 1064.2245439869.

Adding to 1205312921 its reverse (1292135021), we get a palindrome (2497447942).

The spelling of 1205312921 in words is "one billion, two hundred five million, three hundred twelve thousand, nine hundred twenty-one".