31645 has 4 divisors (see below), whose sum is σ = 37980. Its totient is φ = 25312.

The previous prime is 31643. The next prime is 31649. The reversal of 31645 is 54613.

31645 = T₁₁₀ + T₁₁₁ + ... + T₁₁₄.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54613 = 13 ⋅4201.

It can be written as a sum of positive squares in 2 ways, for example, as 17956 + 13689 = 134^2 + 117^2 .

It is a cyclic number.

It is not a de Polignac number, because 31645 - 2¹ = 31643 is a prime.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3160 + ... + 3169.

It is an arithmetic number, because the mean of its divisors is an integer number (9495).

2³¹⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

31645 is a deficient number, since it is larger than the sum of its proper divisors (6335).

31645 is an equidigital number, since it uses as much as digits as its factorization.

31645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6334.

The product of its digits is 360, while the sum is 19.

The square root of 31645 is about 177.8904157058. The cubic root of 31645 is about 31.6301826665.

Subtracting from 31645 its sum of digits (19), we obtain a triangular number (31626 = T₂₅₁).

It can be divided in two parts, 316 and 45, that added together give a square (361 = 19²).

The spelling of 31645 in words is "thirty-one thousand, six hundred forty-five".