31081320 has 160 divisors (see below), whose sum is σ = 107026920. Its totient is φ = 8087040.

The previous prime is 31081319. The next prime is 31081331. The reversal of 31081320 is 2318013.

It can be written as a sum of positive squares in 4 ways, for example, as 18507204 + 12574116 = 4302^2 + 3546^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 31081293 and 31081302.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 171630 + ... + 171810.

Almost surely, 2^31081320 is an apocalyptic number.

31081320 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 31081320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (53513460).

31081320 is an abundant number, since it is smaller than the sum of its proper divisors (75945600).

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

31081320 is a wasteful number, since it uses less digits than its factorization.

31081320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 257 (or 244 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 31081320 is about 5575.0623314901. The cubic root of 31081320 is about 314.4125104281.

Adding to 31081320 its reverse (2318013), we get a palindrome (33399333).

The spelling of 31081320 in words is "thirty-one million, eighty-one thousand, three hundred twenty".