7857942721 has 4 divisors (see below), whose sum is σ = 7870202244. Its totient is φ = 7845683200.

The previous prime is 7857942707. The next prime is 7857942731. The reversal of 7857942721 is 1272497587.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6027814321 + 1830128400 = 77639^2 + 42780^2 .

It is a cyclic number.

It is not a de Polignac number, because 7857942721 - 2¹⁷ = 7857811649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7857942731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6128800 + ... + 6130081.

It is an arithmetic number, because the mean of its divisors is an integer number (1967550561).

Almost surely, 2^7857942721 is an apocalyptic number.

It is an amenable number.

7857942721 is a deficient number, since it is larger than the sum of its proper divisors (12259523).

7857942721 is a wasteful number, since it uses less digits than its factorization.

7857942721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12259522.

The product of its digits is 1975680, while the sum is 52.

The square root of 7857942721 is about 88645.0377686196. The cubic root of 7857942721 is about 1988.0911234912.

The spelling of 7857942721 in words is "seven billion, eight hundred fifty-seven million, nine hundred forty-two thousand, seven hundred twenty-one".