639771 has 8 divisors (see below), whose sum is σ = 930624. Its totient is φ = 387720.

The previous prime is 639757. The next prime is 639833. The reversal of 639771 is 177936.

639771 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 639771 - 2⁵ = 639739 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (33), and also a Moran number because the ratio is a prime number: 19387 = 639771 / (6 + 3 + 9 + 7 + 7 + 1).

It is a nialpdrome in base 15.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639771.

It is not an unprimeable number, because it can be changed into a prime (639701) 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, 9661 + ... + 9726.

It is an arithmetic number, because the mean of its divisors is an integer number (116328).

2⁶³⁹⁷⁷¹ is an apocalyptic number.

639771 is a deficient number, since it is larger than the sum of its proper divisors (290853).

639771 is a wasteful number, since it uses less digits than its factorization.

639771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19401.

The product of its digits is 7938, while the sum is 33.

The square root of 639771 is about 799.8568621947. The cubic root of 639771 is about 86.1671079263.

The spelling of 639771 in words is "six hundred thirty-nine thousand, seven hundred seventy-one".