638906533 has 2 divisors, whose sum is σ = 638906534. Its totient is φ = 638906532.

The previous prime is 638906531. The next prime is 638906537. The reversal of 638906533 is 335609836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 555403489 + 83503044 = 23567^2 + 9138^2 .

It is a cyclic number.

It is not a de Polignac number, because 638906533 - 2¹ = 638906531 is a prime.

Together with 638906531, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 638906533.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638906531) 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, 319453266 + 319453267.

It is an arithmetic number, because the mean of its divisors is an integer number (319453267).

Almost surely, 2^638906533 is an apocalyptic number.

It is an amenable number.

638906533 is a deficient number, since it is larger than the sum of its proper divisors (1).

638906533 is an equidigital number, since it uses as much as digits as its factorization.

638906533 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 349920, while the sum is 43.

The square root of 638906533 is about 25276.6005032322. The cubic root of 638906533 is about 861.2828038929.

The spelling of 638906533 in words is "six hundred thirty-eight million, nine hundred six thousand, five hundred thirty-three".