1221716557 has 2 divisors, whose sum is σ = 1221716558. Its totient is φ = 1221716556.

The previous prime is 1221716527. The next prime is 1221716569. The reversal of 1221716557 is 7556171221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1053262116 + 168454441 = 32454^2 + 12979^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221716557 - 2¹¹ = 1221714509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221716527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610858278 + 610858279.

It is an arithmetic number, because the mean of its divisors is an integer number (610858279).

Almost surely, 2^1221716557 is an apocalyptic number.

It is an amenable number.

1221716557 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221716557 is an equidigital number, since it uses as much as digits as its factorization.

1221716557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 29400, while the sum is 37.

The square root of 1221716557 is about 34953.0621977531. The cubic root of 1221716557 is about 1069.0306406995.

Adding to 1221716557 its reverse (7556171221), we get a palindrome (8777887778).

The spelling of 1221716557 in words is "one billion, two hundred twenty-one million, seven hundred sixteen thousand, five hundred fifty-seven".