1220508721 has 2 divisors, whose sum is σ = 1220508722. Its totient is φ = 1220508720.

The previous prime is 1220508691. The next prime is 1220508743. The reversal of 1220508721 is 1278050221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1008951696 + 211557025 = 31764^2 + 14545^2 .

It is a cyclic number.

It is not a de Polignac number, because 1220508721 - 2²³ = 1212120113 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1220508721.

It is not a weakly prime, because it can be changed into another prime (1220505721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610254360 + 610254361.

It is an arithmetic number, because the mean of its divisors is an integer number (610254361).

Almost surely, 2^1220508721 is an apocalyptic number.

It is an amenable number.

1220508721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1220508721 is an equidigital number, since it uses as much as digits as its factorization.

1220508721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 1220508721 is about 34935.7799540815. The cubic root of 1220508721 is about 1068.6782295956.

Adding to 1220508721 its reverse (1278050221), we get a palindrome (2498558942).

The spelling of 1220508721 in words is "one billion, two hundred twenty million, five hundred eight thousand, seven hundred twenty-one".