639748651 has 4 divisors (see below), whose sum is σ = 640528704. Its totient is φ = 638968600.

The previous prime is 639748609. The next prime is 639748661. The reversal of 639748651 is 156847936.

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

It is a cyclic number.

It is not a de Polignac number, because 639748651 - 2⁷ = 639748523 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639748595 and 639748604.

It is not an unprimeable number, because it can be changed into a prime (639748661) 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 in 3 ways as a sum of consecutive naturals, for example, 388795 + ... + 390436.

It is an arithmetic number, because the mean of its divisors is an integer number (160132176).

Almost surely, 2^639748651 is an apocalyptic number.

639748651 is a deficient number, since it is larger than the sum of its proper divisors (780053).

639748651 is an equidigital number, since it uses as much as digits as its factorization.

639748651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 780052.

The product of its digits is 1088640, while the sum is 49.

The square root of 639748651 is about 25293.2530727070. The cubic root of 639748651 is about 861.6610456147.

The spelling of 639748651 in words is "six hundred thirty-nine million, seven hundred forty-eight thousand, six hundred fifty-one".