7857928721 has 4 divisors (see below), whose sum is σ = 7897416000. Its totient is φ = 7818441444.

The previous prime is 7857928703. The next prime is 7857928723. The reversal of 7857928721 is 1278297587.

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 a cyclic number.

It is not a de Polignac number, because 7857928721 - 2³⁰ = 6784186897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7857928723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19743341 + ... + 19743738.

It is an arithmetic number, because the mean of its divisors is an integer number (1974354000).

Almost surely, 2^7857928721 is an apocalyptic number.

It is an amenable number.

7857928721 is a deficient number, since it is larger than the sum of its proper divisors (39487279).

7857928721 is a wasteful number, since it uses less digits than its factorization.

7857928721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39487278.

The product of its digits is 3951360, while the sum is 56.

The square root of 7857928721 is about 88644.9588019533. The cubic root of 7857928721 is about 1988.0899428051.

The spelling of 7857928721 in words is "seven billion, eight hundred fifty-seven million, nine hundred twenty-eight thousand, seven hundred twenty-one".