• 38 can be written using four 4's:

See also 113.

• 38² = 1444 is the smallest square that contains exactly three digits '4'.

• 38 is the common sum (aka magic constant) of the only magic hexagon of order 3. For example, 38 = 18 + 17 + 3 = 19 + 2 + 4 + 13 = 11 + 6 + 8 + 13.

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38 has 4 divisors (see below), whose sum is σ = 60. Its totient is φ = 18.

The previous prime is 37. The next prime is 41. The reversal of 38 is 83.

Added to its reverse (83) it gives a square (121 = 11²).

38 is nontrivially palindromic in base 4.

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

38 is an esthetic number in base 4, base 5 and base 12, because in such bases its adjacent digits differ by 1.

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

It is a magnanimous number.

It is an Ulam number.

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

38 is an undulating number in base 4.

It is a plaindrome in base 5, base 8, base 10, base 11, base 13, base 14, base 15 and base 16.

It is a nialpdrome in base 7, base 9 and base 12.

It is a congruent number.

It is a pernicious number, because its binary representation contains a prime number (3) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8 + ... + 11.

It is an arithmetic number, because the mean of its divisors is an integer number (15).

38 is a deficient number, since it is larger than the sum of its proper divisors (22).

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

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

The sum of its prime factors is 21.

The product of its digits is 24, while the sum is 11.

The square root of 38 is about 6.1644140030. The cubic root of 38 is about 3.3619754068.

Adding to 38 its sum of digits (11), we get a square (49 = 7²).

Subtracting from 38 its sum of digits (11), we obtain a cube (27 = 3³).

Adding to 38 its reverse (83), we get a palindrome (121).

Subtracting 38 from its reverse (83), we obtain a triangular number (45 = T₉).

The spelling of 38 in words is "thirty-eight", and thus it is an aban number, an oban number, and an uban number.