638521 has 4 divisors (see below), whose sum is σ = 687652. Its totient is φ = 589392.

The previous prime is 638501. The next prime is 638527. The reversal of 638521 is 125836.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 346921 + 291600 = 589^2 + 540^2 .

It is a cyclic number.

It is not a de Polignac number, because 638521 - 2⁵ = 638489 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24546 + ... + 24571.

It is an arithmetic number, because the mean of its divisors is an integer number (171913).

2⁶³⁸⁵²¹ is an apocalyptic number.

It is an amenable number.

638521 is a deficient number, since it is larger than the sum of its proper divisors (49131).

638521 is a wasteful number, since it uses less digits than its factorization.

638521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49130.

The product of its digits is 1440, while the sum is 25.

The square root of 638521 is about 799.0750903388. The cubic root of 638521 is about 86.1109528806.

The spelling of 638521 in words is "six hundred thirty-eight thousand, five hundred twenty-one".