1217166721 has 2 divisors, whose sum is σ = 1217166722. Its totient is φ = 1217166720.

The previous prime is 1217166707. The next prime is 1217166749. The reversal of 1217166721 is 1276617121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1199652496 + 17514225 = 34636^2 + 4185^2 .

It is a cyclic number.

It is not a de Polignac number, because 1217166721 - 2¹³ = 1217158529 is a prime.

It is not a weakly prime, because it can be changed into another prime (1217166751) 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 as a sum of consecutive naturals, namely, 608583360 + 608583361.

It is an arithmetic number, because the mean of its divisors is an integer number (608583361).

Almost surely, 2^1217166721 is an apocalyptic number.

It is an amenable number.

1217166721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1217166721 is an equidigital number, since it uses as much as digits as its factorization.

1217166721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7056, while the sum is 34.

The square root of 1217166721 is about 34887.9165471371. The cubic root of 1217166721 is about 1067.7019188162.

The spelling of 1217166721 in words is "one billion, two hundred seventeen million, one hundred sixty-six thousand, seven hundred twenty-one".