1217808721973 has 4 divisors (see below), whose sum is σ = 1221965066028. Its totient is φ = 1213652377920.

The previous prime is 1217808721931. The next prime is 1217808721979. The reversal of 1217808721973 is 3791278087121.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1195921590724 + 21887131249 = 1093582^2 + 147943^2 .

It is a cyclic number.

It is not a de Polignac number, because 1217808721973 - 2¹² = 1217808717877 is a prime.

It is a super-2 number, since 2×1217808721973² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1217808721979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2078171588 + ... + 2078172173.

It is an arithmetic number, because the mean of its divisors is an integer number (305491266507).

Almost surely, 2^{1217808721973} is an apocalyptic number.

It is an amenable number.

1217808721973 is a deficient number, since it is larger than the sum of its proper divisors (4156344055).

1217808721973 is an equidigital number, since it uses as much as digits as its factorization.

1217808721973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4156344054.

The product of its (nonzero) digits is 2370816, while the sum is 56.

The spelling of 1217808721973 in words is "one trillion, two hundred seventeen billion, eight hundred eight million, seven hundred twenty-one thousand, nine hundred seventy-three".