7987721618 has 6 divisors (see below), whose sum is σ = 11981772021. Its totient is φ = 3993797612.

The previous prime is 7987721617. The next prime is 7987721629. The reversal of 7987721618 is 8161277897.

It can be written as a sum of positive squares in 2 ways, for example, as 4876647889 + 3111073729 = 69833^2 + 55777^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=63197.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7987721617) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 94796 + ... + 157992.

Almost surely, 2^7987721618 is an apocalyptic number.

7987721618 is a deficient number, since it is larger than the sum of its proper divisors (3994050403).

7987721618 is an frugal number, since it uses more digits than its factorization.

7987721618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126396 (or 63199 counting only the distinct ones).

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

The square root of 7987721618 is about 89374.0545012925. The cubic root of 7987721618 is about 1998.9762775856.

The spelling of 7987721618 in words is "seven billion, nine hundred eighty-seven million, seven hundred twenty-one thousand, six hundred eighteen".