7721978321 has 2 divisors, whose sum is σ = 7721978322. Its totient is φ = 7721978320.

The previous prime is 7721978311. The next prime is 7721978359. The reversal of 7721978321 is 1238791277.

7721978321 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7509955600 + 212022721 = 86660^2 + 14561^2 .

It is an emirp because it is prime and its reverse (1238791277) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7721978321 - 2²⁶ = 7654869457 is a prime.

It is not a weakly prime, because it can be changed into another prime (7721978311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3860989160 + 3860989161.

It is an arithmetic number, because the mean of its divisors is an integer number (3860989161).

Almost surely, 2^7721978321 is an apocalyptic number.

It is an amenable number.

7721978321 is a deficient number, since it is larger than the sum of its proper divisors (1).

7721978321 is an equidigital number, since it uses as much as digits as its factorization.

7721978321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 296352, while the sum is 47.

The square root of 7721978321 is about 87874.7877436981. The cubic root of 7721978321 is about 1976.5578326701.

The spelling of 7721978321 in words is "seven billion, seven hundred twenty-one million, nine hundred seventy-eight thousand, three hundred twenty-one".