1221277721 has 4 divisors (see below), whose sum is σ = 1224111744. Its totient is φ = 1218443700.

The previous prime is 1221277711. The next prime is 1221277753. The reversal of 1221277721 is 1277721221.

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.

It is a cyclic number.

It is not a de Polignac number, because 1221277721 - 2¹⁰ = 1221276697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221277711) 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, 1416365 + ... + 1417226.

It is an arithmetic number, because the mean of its divisors is an integer number (306027936).

Almost surely, 2^1221277721 is an apocalyptic number.

It is an amenable number.

1221277721 is a deficient number, since it is larger than the sum of its proper divisors (2834023).

1221277721 is an equidigital number, since it uses as much as digits as its factorization.

1221277721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2834022.

The product of its digits is 5488, while the sum is 32.

The square root of 1221277721 is about 34946.7841295877. The cubic root of 1221277721 is about 1068.9026281070.

Adding to 1221277721 its reverse (1277721221), we get a palindrome (2498998942).

The spelling of 1221277721 in words is "one billion, two hundred twenty-one million, two hundred seventy-seven thousand, seven hundred twenty-one".