31085640 has 128 divisors (see below), whose sum is σ = 104976000. Its totient is φ = 8181504.

The previous prime is 31085633. The next prime is 31085641. The reversal of 31085640 is 4658013.

31085640 is a `hidden beast` number, since 3 + 10 + 8 + 5 + 640 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (31085641) 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 31 ways as a sum of consecutive naturals, for example, 115426 + ... + 115694.

It is an arithmetic number, because the mean of its divisors is an integer number (820125).

Almost surely, 2^31085640 is an apocalyptic number.

31085640 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 31085640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (52488000).

31085640 is an abundant number, since it is smaller than the sum of its proper divisors (73890360).

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

31085640 is a wasteful number, since it uses less digits than its factorization.

31085640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396 (or 386 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 31085640 is about 5575.4497576429. The cubic root of 31085640 is about 314.4270765096.

The spelling of 31085640 in words is "thirty-one million, eighty-five thousand, six hundred forty".