638721228793 has 2 divisors, whose sum is σ = 638721228794. Its totient is φ = 638721228792.

The previous prime is 638721228749. The next prime is 638721228809. The reversal of 638721228793 is 397822127836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 350704393209 + 288016835584 = 592203^2 + 536672^2 .

It is a cyclic number.

It is not a de Polignac number, because 638721228793 - 2¹³ = 638721220601 is a prime.

It is a super-2 number, since 2×638721228793² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (638721268793) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319360614396 + 319360614397.

It is an arithmetic number, because the mean of its divisors is an integer number (319360614397).

Almost surely, 2^638721228793 is an apocalyptic number.

It is an amenable number.

638721228793 is a deficient number, since it is larger than the sum of its proper divisors (1).

638721228793 is an equidigital number, since it uses as much as digits as its factorization.

638721228793 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12192768, while the sum is 58.

The spelling of 638721228793 in words is "six hundred thirty-eight billion, seven hundred twenty-one million, two hundred twenty-eight thousand, seven hundred ninety-three".