639481 has 4 divisors (see below), whose sum is σ = 641872. Its totient is φ = 637092.

The previous prime is 639451. The next prime is 639487. The reversal of 639481 is 184936.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639481 is a prime.

It is a super-2 number, since 2×639481² = 817871898722, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (639487) 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, 735 + ... + 1348.

It is an arithmetic number, because the mean of its divisors is an integer number (160468).

2⁶³⁹⁴⁸¹ is an apocalyptic number.

It is an amenable number.

639481 is a deficient number, since it is larger than the sum of its proper divisors (2391).

639481 is a wasteful number, since it uses less digits than its factorization.

639481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2390.

The product of its digits is 5184, while the sum is 31.

The square root of 639481 is about 799.6755592114. The cubic root of 639481 is about 86.1540864765.

The spelling of 639481 in words is "six hundred thirty-nine thousand, four hundred eighty-one".