8403721 has 2 divisors, whose sum is σ = 8403722. Its totient is φ = 8403720.

The previous prime is 8403709. The next prime is 8403727. The reversal of 8403721 is 1273048.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4999696 + 3404025 = 2236^2 + 1845^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8403721 is a prime.

It is not a weakly prime, because it can be changed into another prime (8403727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4201860 + 4201861.

It is an arithmetic number, because the mean of its divisors is an integer number (4201861).

Almost surely, 2^8403721 is an apocalyptic number.

It is an amenable number.

8403721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8403721 is an equidigital number, since it uses as much as digits as its factorization.

8403721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 8403721 is about 2898.9172116499. The cubic root of 8403721 is about 203.3092828910.

Adding to 8403721 its reverse (1273048), we get a palindrome (9676769).

The spelling of 8403721 in words is "eight million, four hundred three thousand, seven hundred twenty-one".