9721638449 has 2 divisors, whose sum is σ = 9721638450. Its totient is φ = 9721638448.

The previous prime is 9721638431. The next prime is 9721638457. The reversal of 9721638449 is 9448361279.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9373144225 + 348494224 = 96815^2 + 18668^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9721638449 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 9721638449.

It is not a weakly prime, because it can be changed into another prime (9721638499) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4860819224 + 4860819225.

It is an arithmetic number, because the mean of its divisors is an integer number (4860819225).

Almost surely, 2^9721638449 is an apocalyptic number.

It is an amenable number.

9721638449 is a deficient number, since it is larger than the sum of its proper divisors (1).

9721638449 is an equidigital number, since it uses as much as digits as its factorization.

9721638449 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2612736, while the sum is 53.

The square root of 9721638449 is about 98598.3694033527. The cubic root of 9721638449 is about 2134.2558892960.

The spelling of 9721638449 in words is "nine billion, seven hundred twenty-one million, six hundred thirty-eight thousand, four hundred forty-nine".