638540 has 24 divisors (see below), whose sum is σ = 1532832. Its totient is φ = 218880.

The previous prime is 638527. The next prime is 638567. The reversal of 638540 is 45836.

638540 = T₂₉₅ + T₂₉₆ + ... + T₃₀₈.

It is a congruent number.

It is an unprimeable number.

638540 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 7 ways as a sum of consecutive naturals, for example, 2141 + ... + 2420.

It is an arithmetic number, because the mean of its divisors is an integer number (63868).

2⁶³⁸⁵⁴⁰ is an apocalyptic number.

It is an amenable number.

638540 is an abundant number, since it is smaller than the sum of its proper divisors (894292).

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

638540 is a wasteful number, since it uses less digits than its factorization.

638540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4577 (or 4575 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 638540 is about 799.0869789954. The cubic root of 638540 is about 86.1118069856. Note that the first 3 decimals are identical.

Subtracting from 638540 its reverse (45836), we obtain a cube (592704 = 84³).

The spelling of 638540 in words is "six hundred thirty-eight thousand, five hundred forty".