1211221021 has 4 divisors (see below), whose sum is σ = 1228280544. Its totient is φ = 1194161500.

The previous prime is 1211221019. The next prime is 1211221043. The reversal of 1211221021 is 1201221121.

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 an emirpimes, since its reverse is a distinct semiprime: 1201221121 = 227 ⋅5291723.

It is a cyclic number.

It is not a de Polignac number, because 1211221021 - 2¹ = 1211221019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1211220992 and 1211221010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211221091) 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, 8529655 + ... + 8529796.

It is an arithmetic number, because the mean of its divisors is an integer number (307070136).

Almost surely, 2^1211221021 is an apocalyptic number.

It is an amenable number.

1211221021 is a deficient number, since it is larger than the sum of its proper divisors (17059523).

1211221021 is an equidigital number, since it uses as much as digits as its factorization.

1211221021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17059522.

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 1211221021 is about 34802.6007792521. The cubic root of 1211221021 is about 1065.9605522752.

Adding to 1211221021 its reverse (1201221121), we get a palindrome (2412442142).

It can be divided in two parts, 12112 and 21021, that added together give a palindrome (33133).

The spelling of 1211221021 in words is "one billion, two hundred eleven million, two hundred twenty-one thousand, twenty-one".