639771044 has 18 divisors (see below), whose sum is σ = 1230634902. Its totient is φ = 290804800.

The previous prime is 639771029. The next prime is 639771049. The reversal of 639771044 is 440177936.

It can be written as a sum of positive squares in only one way, i.e., 634536100 + 5234944 = 25190^2 + 2288^2 .

It is a junction number, because it is equal to n+sod(n) for n = 639770992 and 639771010.

It is not an unprimeable number, because it can be changed into a prime (639771049) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 660437 + ... + 661404.

Almost surely, 2^639771044 is an apocalyptic number.

It is an amenable number.

639771044 is a deficient number, since it is larger than the sum of its proper divisors (590863858).

639771044 is a wasteful number, since it uses less digits than its factorization.

639771044 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1321867 (or 1321854 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 41.

The square root of 639771044 is about 25293.6957362897. The cubic root of 639771044 is about 861.6710990165.

The spelling of 639771044 in words is "six hundred thirty-nine million, seven hundred seventy-one thousand, forty-four".