7891221987 has 64 divisors (see below), whose sum is σ = 13887936000. Its totient is φ = 4374518400.

The previous prime is 7891221973. The next prime is 7891222021.

7891221987 is nontrivially palindromic in base 10.

7891221987 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 7891221987 - 2⁴ = 7891221971 is a prime.

It is a super-2 number, since 2×7891221987² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (7891221917) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 139537 + ... + 187757.

It is an arithmetic number, because the mean of its divisors is an integer number (216999000).

Almost surely, 2^7891221987 is an apocalyptic number.

7891221987 is a deficient number, since it is larger than the sum of its proper divisors (5996714013).

7891221987 is a wasteful number, since it uses less digits than its factorization.

7891221987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48289 (or 48283 counting only the distinct ones).

The product of its digits is 1016064, while the sum is 54.

The square root of 7891221987 is about 88832.5502673429. The cubic root of 7891221987 is about 1990.8937667682.

The spelling of 7891221987 in words is "seven billion, eight hundred ninety-one million, two hundred twenty-one thousand, nine hundred eighty-seven".