7821279845 has 16 divisors (see below), whose sum is σ = 10280306160. Its totient is φ = 5685894144.

The previous prime is 7821279827. The next prime is 7821279853. The reversal of 7821279845 is 5489721287.

It is a Cunningham number, because it is equal to 88438²+1.

It can be written as a sum of positive squares in 8 ways, for example, as 773173636 + 7048106209 = 27806^2 + 83953^2 .

It is a cyclic number.

It is not a de Polignac number, because 7821279845 - 2¹⁰ = 7821278821 is a prime.

It is a super-2 number, since 2×7821279845² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1584002 + ... + 1588931.

It is an arithmetic number, because the mean of its divisors is an integer number (642519135).

Almost surely, 2^7821279845 is an apocalyptic number.

It is an amenable number.

7821279845 is a deficient number, since it is larger than the sum of its proper divisors (2459026315).

7821279845 is a wasteful number, since it uses less digits than its factorization.

7821279845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3172984.

The product of its digits is 2257920, while the sum is 53.

The square root of 7821279845 is about 88438.0000056537. Note that the first 5 decimals coincide. The cubic root of 7821279845 is about 1984.9943505603.

The spelling of 7821279845 in words is "seven billion, eight hundred twenty-one million, two hundred seventy-nine thousand, eight hundred forty-five".