8656721 has 2 divisors, whose sum is σ = 8656722. Its totient is φ = 8656720.

The previous prime is 8656691. The next prime is 8656727. The reversal of 8656721 is 1276568.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8526400 + 130321 = 2920^2 + 361^2 .

It is a cyclic number.

It is not a de Polignac number, because 8656721 - 2¹⁴ = 8640337 is a prime.

It is a super-3 number, since 3×8656721³ (a number of 22 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (8656727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4328360 + 4328361.

It is an arithmetic number, because the mean of its divisors is an integer number (4328361).

Almost surely, 2^8656721 is an apocalyptic number.

It is an amenable number.

8656721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8656721 is an equidigital number, since it uses as much as digits as its factorization.

8656721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20160, while the sum is 35.

The square root of 8656721 is about 2942.2306163861. The cubic root of 8656721 is about 205.3294010205.

The spelling of 8656721 in words is "eight million, six hundred fifty-six thousand, seven hundred twenty-one".