638998 has 4 divisors (see below), whose sum is σ = 958500. Its totient is φ = 319498.

The previous prime is 638993. The next prime is 638999. The reversal of 638998 is 899836.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638993) by changing a digit.

638998 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 (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159748 + ... + 159751.

It is an arithmetic number, because the mean of its divisors is an integer number (239625).

2⁶³⁸⁹⁹⁸ is an apocalyptic number.

638998 is a deficient number, since it is larger than the sum of its proper divisors (319502).

638998 is a wasteful number, since it uses less digits than its factorization.

638998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319501.

The product of its digits is 93312, while the sum is 43.

The square root of 638998 is about 799.3735046898. The cubic root of 638998 is about 86.1323902860.

The spelling of 638998 in words is "six hundred thirty-eight thousand, nine hundred ninety-eight".