31138 has 4 divisors (see below), whose sum is σ = 46710. Its totient is φ = 15568.

The previous prime is 31123. The next prime is 31139. The reversal of 31138 is 83113.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 83113 = 17 ⋅4889.

It can be written as a sum of positive squares in only one way, i.e., 27889 + 3249 = 167^2 + 57^2 .

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (31139) by changing a digit.

31138 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7783 + ... + 7786.

2³¹¹³⁸ is an apocalyptic number.

31138 is a deficient number, since it is larger than the sum of its proper divisors (15572).

31138 is a wasteful number, since it uses less digits than its factorization.

31138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15571.

The product of its digits is 72, while the sum is 16.

The square root of 31138 is about 176.4596271106. The cubic root of 31138 is about 31.4603515607.

It can be divided in two parts, 31 and 138, that multiplied together give a triangular number (4278 = T₉₂).

The spelling of 31138 in words is "thirty-one thousand, one hundred thirty-eight".