638748757 has 4 divisors (see below), whose sum is σ = 639715756. Its totient is φ = 637781760.

The previous prime is 638748689. The next prime is 638748767. The reversal of 638748757 is 757847836.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 514337041 + 124411716 = 22679^2 + 11154^2 .

It is a cyclic number.

It is not a de Polignac number, because 638748757 - 2¹¹ = 638746709 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 638748698 and 638748707.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638748767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 482508 + ... + 483829.

It is an arithmetic number, because the mean of its divisors is an integer number (159928939).

Almost surely, 2^638748757 is an apocalyptic number.

It is an amenable number.

638748757 is a deficient number, since it is larger than the sum of its proper divisors (966999).

638748757 is an equidigital number, since it uses as much as digits as its factorization.

638748757 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 966998.

The product of its digits is 7902720, while the sum is 55.

The square root of 638748757 is about 25273.4793212173. The cubic root of 638748757 is about 861.2119010112.

The spelling of 638748757 in words is "six hundred thirty-eight million, seven hundred forty-eight thousand, seven hundred fifty-seven".