31645728 has 120 divisors (see below), whose sum is σ = 96507180. Its totient is φ = 10160640.

The previous prime is 31645709. The next prime is 31645729. The reversal of 31645728 is 82754613.

31645728 is a `hidden beast` number, since 3 + 1 + 645 + 7 + 2 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 28005264 + 3640464 = 5292^2 + 1908^2 .

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 = 31645692 and 31645701.

It is not an unprimeable number, because it can be changed into a prime (31645729) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 74958 + ... + 75378.

Almost surely, 2^31645728 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 31645728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (48253590).

31645728 is an abundant number, since it is smaller than the sum of its proper divisors (64861452).

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

31645728 is a wasteful number, since it uses less digits than its factorization.

31645728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 472 (or 455 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 31645728 is about 5625.4535817123. The cubic root of 31645728 is about 316.3042521767.

The spelling of 31645728 in words is "thirty-one million, six hundred forty-five thousand, seven hundred twenty-eight".