8439721 has 2 divisors, whose sum is σ = 8439722. Its totient is φ = 8439720.

The previous prime is 8439713. The next prime is 8439751. The reversal of 8439721 is 1279348.

8439721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6579225 + 1860496 = 2565^2 + 1364^2 .

It is a cyclic number.

It is not a de Polignac number, because 8439721 - 2³ = 8439713 is a prime.

It is not a weakly prime, because it can be changed into another prime (8439751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4219860 + 4219861.

It is an arithmetic number, because the mean of its divisors is an integer number (4219861).

Almost surely, 2^8439721 is an apocalyptic number.

It is an amenable number.

8439721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8439721 is an equidigital number, since it uses as much as digits as its factorization.

8439721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 34.

The square root of 8439721 is about 2905.1197909897. The cubic root of 8439721 is about 203.5991825561.

The spelling of 8439721 in words is "eight million, four hundred thirty-nine thousand, seven hundred twenty-one".