31540 has 24 divisors (see below), whose sum is σ = 70560. Its totient is φ = 11808.

The previous prime is 31531. The next prime is 31541. The reversal of 31540 is 4513.

31540 = T₁₈ + T₁₉ + ... + T₅₇.

It is a self number, because there is not a number n which added to its sum of digits gives 31540.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31541) by changing a digit.

31540 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 in 7 ways as a sum of consecutive naturals, for example, 339 + ... + 421.

It is an arithmetic number, because the mean of its divisors is an integer number (2940).

2³¹⁵⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35280).

31540 is an abundant number, since it is smaller than the sum of its proper divisors (39020).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

31540 is a wasteful number, since it uses less digits than its factorization.

31540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111 (or 109 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 13.

The square root of 31540 is about 177.5950449759. The cubic root of 31540 is about 31.5951602907.

The spelling of 31540 in words is "thirty-one thousand, five hundred forty".