31131540 has 120 divisors (see below), whose sum is σ = 106600032. Its totient is φ = 7542720.

The previous prime is 31131497. The next prime is 31131547. The reversal of 31131540 is 4513113.

31131540 is a `hidden beast` number, since 311 + 315 + 40 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31131547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 16947 + ... + 18693.

Almost surely, 2^31131540 is an apocalyptic number.

31131540 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31131540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (53300016).

31131540 is an abundant number, since it is smaller than the sum of its proper divisors (75468492).

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

31131540 is a wasteful number, since it uses less digits than its factorization.

31131540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1779 (or 1768 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 31131540 is about 5579.5644991343. The cubic root of 31131540 is about 314.5817578487.

Adding to 31131540 its reverse (4513113), we get a palindrome (35644653).

The spelling of 31131540 in words is "thirty-one million, one hundred thirty-one thousand, five hundred forty".