31665728 has 28 divisors (see below), whose sum is σ = 63642240. Its totient is φ = 15629952.

The previous prime is 31665727. The next prime is 31665737. The reversal of 31665728 is 82756613.

It is a super-3 number, since 3×31665728³ (a number of 23 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 31665691 and 31665700.

It is not an unprimeable number, because it can be changed into a prime (31665727) 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 3 ways as a sum of consecutive naturals, for example, 1925 + ... + 8187.

Almost surely, 2^31665728 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 31665728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31821120).

31665728 is an abundant number, since it is smaller than the sum of its proper divisors (31976512).

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

31665728 is an equidigital number, since it uses as much as digits as its factorization.

31665728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6354 (or 6344 counting only the distinct ones).

The product of its digits is 60480, while the sum is 38.

The square root of 31665728 is about 5627.2309353713. The cubic root of 31665728 is about 316.3708725730.

The spelling of 31665728 in words is "thirty-one million, six hundred sixty-five thousand, seven hundred twenty-eight".