7821208985 has 4 divisors (see below), whose sum is σ = 9385450788. Its totient is φ = 6256967184.

The previous prime is 7821208957. The next prime is 7821208987. The reversal of 7821208985 is 5898021287.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5898021287 = 19 ⋅310422173.

It can be written as a sum of positive squares in 2 ways, for example, as 862479424 + 6958729561 = 29368^2 + 83419^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7821208985 is a prime.

It is a super-2 number, since 2×7821208985² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7821208987) 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 in 3 ways as a sum of consecutive naturals, for example, 782120894 + ... + 782120903.

It is an arithmetic number, because the mean of its divisors is an integer number (2346362697).

Almost surely, 2^7821208985 is an apocalyptic number.

It is an amenable number.

7821208985 is a deficient number, since it is larger than the sum of its proper divisors (1564241803).

7821208985 is a wasteful number, since it uses less digits than its factorization.

7821208985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1564241802.

The product of its (nonzero) digits is 645120, while the sum is 50.

The square root of 7821208985 is about 88437.5993851032. The cubic root of 7821208985 is about 1984.9883559266.

The spelling of 7821208985 in words is "seven billion, eight hundred twenty-one million, two hundred eight thousand, nine hundred eighty-five".