7931865821 has 4 divisors (see below), whose sum is σ = 8652944544. Its totient is φ = 7210787100.

The previous prime is 7931865811. The next prime is 7931865829. The reversal of 7931865821 is 1285681397.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 7931865821 - 2⁶ = 7931865757 is a prime.

It is a super-3 number, since 3×7931865821³ (a number of 31 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 7931865821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7931865829) 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, 360539345 + ... + 360539366.

It is an arithmetic number, because the mean of its divisors is an integer number (2163236136).

Almost surely, 2^7931865821 is an apocalyptic number.

It is an amenable number.

7931865821 is a deficient number, since it is larger than the sum of its proper divisors (721078723).

7931865821 is a wasteful number, since it uses less digits than its factorization.

7931865821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 721078722.

The product of its digits is 725760, while the sum is 50.

The square root of 7931865821 is about 89061.0230179286. The cubic root of 7931865821 is about 1994.3059560663.

The spelling of 7931865821 in words is "seven billion, nine hundred thirty-one million, eight hundred sixty-five thousand, eight hundred twenty-one".