638820001 has 2 divisors, whose sum is σ = 638820002. Its totient is φ = 638820000.

The previous prime is 638819947. The next prime is 638820019. The reversal of 638820001 is 100028836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 449482401 + 189337600 = 21201^2 + 13760^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638820001 is a prime.

It is not a weakly prime, because it can be changed into another prime (638020001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319410000 + 319410001.

It is an arithmetic number, because the mean of its divisors is an integer number (319410001).

Almost surely, 2^638820001 is an apocalyptic number.

It is an amenable number.

638820001 is a deficient number, since it is larger than the sum of its proper divisors (1).

638820001 is an equidigital number, since it uses as much as digits as its factorization.

638820001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 638820001 is about 25274.8887435731. Note that the first 3 decimals coincide. The cubic root of 638820001 is about 861.2439187641.

Adding to 638820001 its reverse (100028836), we get a palindrome (738848837).

The spelling of 638820001 in words is "six hundred thirty-eight million, eight hundred twenty thousand, one".