1221221021 has 4 divisors (see below), whose sum is σ = 1223126844. Its totient is φ = 1219315200.

The previous prime is 1221221003. The next prime is 1221221033. The reversal of 1221221021 is 1201221221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1201221221 = 3109 ⋅386369.

It can be written as a sum of positive squares in 2 ways, for example, as 917241796 + 303979225 = 30286^2 + 17435^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221221021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221220987 and 1221221005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221221051) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 951950 + ... + 953231.

It is an arithmetic number, because the mean of its divisors is an integer number (305781711).

Almost surely, 2^1221221021 is an apocalyptic number.

It is an amenable number.

1221221021 is a deficient number, since it is larger than the sum of its proper divisors (1905823).

1221221021 is an equidigital number, since it uses as much as digits as its factorization.

1221221021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1905822.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 1221221021 is about 34945.9728867290. The cubic root of 1221221021 is about 1068.8860859463.

Adding to 1221221021 its reverse (1201221221), we get a palindrome (2422442242).

It can be divided in two parts, 12212 and 21021, that added together give a palindrome (33233).

The spelling of 1221221021 in words is "one billion, two hundred twenty-one million, two hundred twenty-one thousand, twenty-one".