638242133 has 2 divisors, whose sum is σ = 638242134. Its totient is φ = 638242132.

The previous prime is 638242109. The next prime is 638242141. The reversal of 638242133 is 331242836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 373919569 + 264322564 = 19337^2 + 16258^2 .

It is a cyclic number.

It is not a de Polignac number, because 638242133 - 2⁶ = 638242069 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 638242133.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638242733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319121066 + 319121067.

It is an arithmetic number, because the mean of its divisors is an integer number (319121067).

Almost surely, 2^638242133 is an apocalyptic number.

It is an amenable number.

638242133 is a deficient number, since it is larger than the sum of its proper divisors (1).

638242133 is an equidigital number, since it uses as much as digits as its factorization.

638242133 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 32.

The square root of 638242133 is about 25263.4544945857. The cubic root of 638242133 is about 860.9841505237.

Adding to 638242133 its reverse (331242836), we get a palindrome (969484969).

The spelling of 638242133 in words is "six hundred thirty-eight million, two hundred forty-two thousand, one hundred thirty-three".