9928638721 has 2 divisors, whose sum is σ = 9928638722. Its totient is φ = 9928638720.

The previous prime is 9928638703. The next prime is 9928638757. The reversal of 9928638721 is 1278368299.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6396000625 + 3532638096 = 79975^2 + 59436^2 .

It is a cyclic number.

It is not a de Polignac number, because 9928638721 - 2¹¹ = 9928636673 is a prime.

It is not a weakly prime, because it can be changed into another prime (9928638701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4964319360 + 4964319361.

It is an arithmetic number, because the mean of its divisors is an integer number (4964319361).

Almost surely, 2^9928638721 is an apocalyptic number.

It is an amenable number.

9928638721 is a deficient number, since it is larger than the sum of its proper divisors (1).

9928638721 is an equidigital number, since it uses as much as digits as its factorization.

9928638721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2612736, while the sum is 55.

The square root of 9928638721 is about 99642.5547695361. The cubic root of 9928638721 is about 2149.2976772913.

The spelling of 9928638721 in words is "nine billion, nine hundred twenty-eight million, six hundred thirty-eight thousand, seven hundred twenty-one".