8947721 has 2 divisors, whose sum is σ = 8947722. Its totient is φ = 8947720.

The previous prime is 8947709. The next prime is 8947723. The reversal of 8947721 is 1277498.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5125696 + 3822025 = 2264^2 + 1955^2 .

It is a cyclic number.

It is not a de Polignac number, because 8947721 - 2⁶ = 8947657 is a prime.

It is a super-2 number, since 2×8947721² = 160123422187682, which contains 22 as substring.

Together with 8947723, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (8947723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4473860 + 4473861.

It is an arithmetic number, because the mean of its divisors is an integer number (4473861).

Almost surely, 2^8947721 is an apocalyptic number.

It is an amenable number.

8947721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8947721 is an equidigital number, since it uses as much as digits as its factorization.

8947721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 28224, while the sum is 38.

The square root of 8947721 is about 2991.2741432373. The cubic root of 8947721 is about 207.6048417783.

It can be divided in two parts, 89477 and 21, that added together give a palindrome (89498).

The spelling of 8947721 in words is "eight million, nine hundred forty-seven thousand, seven hundred twenty-one".