638761 has 4 divisors (see below), whose sum is σ = 672400. Its totient is φ = 605124.

The previous prime is 638719. The next prime is 638767. The reversal of 638761 is 167836.

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 638761 - 2⁷ = 638633 is a prime.

It is an Ulam number.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638767) 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, 16791 + ... + 16828.

It is an arithmetic number, because the mean of its divisors is an integer number (168100).

2⁶³⁸⁷⁶¹ is an apocalyptic number.

It is an amenable number.

638761 is a deficient number, since it is larger than the sum of its proper divisors (33639).

638761 is a wasteful number, since it uses less digits than its factorization.

638761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33638.

The product of its digits is 6048, while the sum is 31.

The square root of 638761 is about 799.2252498514. The cubic root of 638761 is about 86.1217403305.

Adding to 638761 its product of digits (6048), we get a square (644809 = 803²).

The spelling of 638761 in words is "six hundred thirty-eight thousand, seven hundred sixty-one".