8557721 has 2 divisors, whose sum is σ = 8557722. Its totient is φ = 8557720.

The previous prime is 8557711. The next prime is 8557723. The reversal of 8557721 is 1277558.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7425625 + 1132096 = 2725^2 + 1064^2 .

It is a cyclic number.

It is not a de Polignac number, because 8557721 - 2¹⁰ = 8556697 is a prime.

Together with 8557723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (8557723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4278860 + 4278861.

It is an arithmetic number, because the mean of its divisors is an integer number (4278861).

Almost surely, 2^8557721 is an apocalyptic number.

It is an amenable number.

8557721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8557721 is an equidigital number, since it uses as much as digits as its factorization.

8557721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19600, while the sum is 35.

The square root of 8557721 is about 2925.3582686570. The cubic root of 8557721 is about 204.5436686773.

The spelling of 8557721 in words is "eight million, five hundred fifty-seven thousand, seven hundred twenty-one".