999638 has 4 divisors (see below), whose sum is σ = 1499460. Its totient is φ = 499818.

The previous prime is 999631. The next prime is 999653. The reversal of 999638 is 836999.

999638 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 836999 = 569 ⋅1471.

It is a super-2 number, since 2×999638² = 1998552262088, which contains 22 as substring.

It is an Ulam number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 999638.

It is not an unprimeable number, because it can be changed into a prime (999631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 249908 + ... + 249911.

It is an arithmetic number, because the mean of its divisors is an integer number (374865).

2⁹⁹⁹⁶³⁸ is an apocalyptic number.

999638 is a deficient number, since it is larger than the sum of its proper divisors (499822).

999638 is a wasteful number, since it uses less digits than its factorization.

999638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 499821.

The product of its digits is 104976, while the sum is 44.

The square root of 999638 is about 999.8189836165. The cubic root of 999638 is about 99.9879318770.

The spelling of 999638 in words is "nine hundred ninety-nine thousand, six hundred thirty-eight".