31985640 has 96 divisors (see below), whose sum is σ = 108501120. Its totient is φ = 8156544.

The previous prime is 31985633. The next prime is 31985647. The reversal of 31985640 is 4658913.

31985640 is a `hidden beast` number, since 3 + 1 + 9 + 8 + 5 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (31985633) and next prime (31985647).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 31985595 and 31985604.

It is not an unprimeable number, because it can be changed into a prime (31985647) 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 23 ways as a sum of consecutive naturals, for example, 6349 + ... + 10211.

It is an arithmetic number, because the mean of its divisors is an integer number (1130220).

Almost surely, 2^31985640 is an apocalyptic number.

31985640 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 31985640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (54250560).

31985640 is an abundant number, since it is smaller than the sum of its proper divisors (76515480).

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

31985640 is a wasteful number, since it uses less digits than its factorization.

31985640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3903 (or 3896 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 31985640 is about 5655.5848503935. The cubic root of 31985640 is about 317.4327135401.

The spelling of 31985640 in words is "thirty-one million, nine hundred eighty-five thousand, six hundred forty".