1217821993 has 2 divisors, whose sum is σ = 1217821994. Its totient is φ = 1217821992.

The previous prime is 1217821987. The next prime is 1217822017. The reversal of 1217821993 is 3991287121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1147312384 + 70509609 = 33872^2 + 8397^2 .

It is an emirp because it is prime and its reverse (3991287121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1217821993 - 2⁵ = 1217821961 is a prime.

It is not a weakly prime, because it can be changed into another prime (1217821933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608910996 + 608910997.

It is an arithmetic number, because the mean of its divisors is an integer number (608910997).

Almost surely, 2^1217821993 is an apocalyptic number.

It is an amenable number.

1217821993 is a deficient number, since it is larger than the sum of its proper divisors (1).

1217821993 is an equidigital number, since it uses as much as digits as its factorization.

1217821993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432, while the sum is 43.

The square root of 1217821993 is about 34897.3063860235. The cubic root of 1217821993 is about 1067.8934865628.

The spelling of 1217821993 in words is "one billion, two hundred seventeen million, eight hundred twenty-one thousand, nine hundred ninety-three".