639618 has 32 divisors (see below), whose sum is σ = 1486464. Its totient is φ = 179712.

The previous prime is 639601. The next prime is 639631. The reversal of 639618 is 816936.

It is a super-2 number, since 2×639618² = 818222371848, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3996 + ... + 4152.

It is an arithmetic number, because the mean of its divisors is an integer number (46452).

2⁶³⁹⁶¹⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639618, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (743232).

639618 is an abundant number, since it is smaller than the sum of its proper divisors (846846).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639618 is a wasteful number, since it uses less digits than its factorization.

639618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266.

The product of its digits is 7776, while the sum is 33.

The square root of 639618 is about 799.7612143634. The cubic root of 639618 is about 86.1602384795.

The spelling of 639618 in words is "six hundred thirty-nine thousand, six hundred eighteen".