639509945 has 8 divisors (see below), whose sum is σ = 776035080. Its totient is φ = 505859200.

The previous prime is 639509929. The next prime is 639509947. The reversal of 639509945 is 549905936.

639509945 is digitally balanced in base 2 and base 6, because in such bases it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 9048064 + 630461881 = 3008^2 + 25109^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 639509945 - 2⁴ = 639509929 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 639509893 and 639509902.

It is not an unprimeable number, because it can be changed into a prime (639509947) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 718106 + ... + 718995.

It is an arithmetic number, because the mean of its divisors is an integer number (97004385).

Almost surely, 2^639509945 is an apocalyptic number.

It is an amenable number.

639509945 is a deficient number, since it is larger than the sum of its proper divisors (136525135).

639509945 is a wasteful number, since it uses less digits than its factorization.

639509945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1437195.

The product of its (nonzero) digits is 1312200, while the sum is 50.

The square root of 639509945 is about 25288.5338641844. The cubic root of 639509945 is about 861.5538632870.

The spelling of 639509945 in words is "six hundred thirty-nine million, five hundred nine thousand, nine hundred forty-five".