638641 has 4 divisors (see below), whose sum is σ = 666432. Its totient is φ = 610852.

The previous prime is 638633. The next prime is 638663. The reversal of 638641 is 146836.

638641 is nontrivially palindromic in base 5.

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 not a de Polignac number, because 638641 - 2³ = 638633 is a prime.

It is a Duffinian number.

638641 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638621) 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, 13861 + ... + 13906.

It is an arithmetic number, because the mean of its divisors is an integer number (166608).

2⁶³⁸⁶⁴¹ is an apocalyptic number.

It is an amenable number.

638641 is a deficient number, since it is larger than the sum of its proper divisors (27791).

638641 is a wasteful number, since it uses less digits than its factorization.

638641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27790.

The product of its digits is 3456, while the sum is 28.

The square root of 638641 is about 799.1501736220. The cubic root of 638641 is about 86.1163469434.

The spelling of 638641 in words is "six hundred thirty-eight thousand, six hundred forty-one".