7857221 has 4 divisors (see below), whose sum is σ = 7886700. Its totient is φ = 7827744.

The previous prime is 7857211. The next prime is 7857233. The reversal of 7857221 is 1227587.

7857221 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1227587 = 17 ⋅72211.

It can be written as a sum of positive squares in 2 ways, for example, as 1677025 + 6180196 = 1295^2 + 2486^2 .

It is a cyclic number.

It is not a de Polignac number, because 7857221 - 2¹⁰ = 7856197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7857211) 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 in 3 ways as a sum of consecutive naturals, for example, 14336 + ... + 14873.

It is an arithmetic number, because the mean of its divisors is an integer number (1971675).

Almost surely, 2^7857221 is an apocalyptic number.

It is an amenable number.

7857221 is a deficient number, since it is larger than the sum of its proper divisors (29479).

7857221 is a wasteful number, since it uses less digits than its factorization.

7857221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29478.

The product of its digits is 7840, while the sum is 32.

The square root of 7857221 is about 2803.0734917230. The cubic root of 7857221 is about 198.8030255522.

The spelling of 7857221 in words is "seven million, eight hundred fifty-seven thousand, two hundred twenty-one".