1221021313 has 4 divisors (see below), whose sum is σ = 1221099568. Its totient is φ = 1220943060.

The previous prime is 1221021299. The next prime is 1221021337. The reversal of 1221021313 is 3131201221.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 3131201221 = 31 ⋅101006491.

It is a cyclic number.

It is not a de Polignac number, because 1221021313 - 2⁵ = 1221021281 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221021913) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6843 + ... + 49888.

It is an arithmetic number, because the mean of its divisors is an integer number (305274892).

Almost surely, 2^1221021313 is an apocalyptic number.

It is an amenable number.

1221021313 is a deficient number, since it is larger than the sum of its proper divisors (78255).

1221021313 is an equidigital number, since it uses as much as digits as its factorization.

1221021313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78254.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 1221021313 is about 34943.1153877270. The cubic root of 1221021313 is about 1068.8278172857.

Adding to 1221021313 its reverse (3131201221), we get a palindrome (4352222534).

The spelling of 1221021313 in words is "one billion, two hundred twenty-one million, twenty-one thousand, three hundred thirteen".