638758261 has 2 divisors, whose sum is σ = 638758262. Its totient is φ = 638758260.

The previous prime is 638758259. The next prime is 638758291. The reversal of 638758261 is 162857836.

638758261 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 601181361 + 37576900 = 24519^2 + 6130^2 .

It is a cyclic number.

It is not a de Polignac number, because 638758261 - 2¹ = 638758259 is a prime.

Together with 638758259, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638758201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319379130 + 319379131.

It is an arithmetic number, because the mean of its divisors is an integer number (319379131).

Almost surely, 2^638758261 is an apocalyptic number.

It is an amenable number.

638758261 is a deficient number, since it is larger than the sum of its proper divisors (1).

638758261 is an equidigital number, since it uses as much as digits as its factorization.

638758261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 483840, while the sum is 46.

The square root of 638758261 is about 25273.6673436998. The cubic root of 638758261 is about 861.2161723397.

The spelling of 638758261 in words is "six hundred thirty-eight million, seven hundred fifty-eight thousand, two hundred sixty-one".