7987921921 has 8 divisors (see below), whose sum is σ = 9200936960. Its totient is φ = 6792877728.

The previous prime is 7987921867. The next prime is 7987921969. The reversal of 7987921921 is 1291297897.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 7987921921 - 2¹¹ = 7987919873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7987921021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4491756 + ... + 4493533.

It is an arithmetic number, because the mean of its divisors is an integer number (1150117120).

Almost surely, 2^7987921921 is an apocalyptic number.

It is an amenable number.

7987921921 is a deficient number, since it is larger than the sum of its proper divisors (1213015039).

7987921921 is a wasteful number, since it uses less digits than its factorization.

7987921921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8985423.

The product of its digits is 1143072, while the sum is 55.

The square root of 7987921921 is about 89375.1750823460. The cubic root of 7987921921 is about 1998.9929864636.

The spelling of 7987921921 in words is "seven billion, nine hundred eighty-seven million, nine hundred twenty-one thousand, nine hundred twenty-one".