31321728 has 192 divisors, whose sum is σ = 100245600. Its totient is φ = 9704448.

The previous prime is 31321727. The next prime is 31321739. The reversal of 31321728 is 82712313.

It is a tau number, because it is divible by the number of its divisors (192).

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 (31321727) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 590950 + ... + 591002.

Almost surely, 2^31321728 is an apocalyptic number.

31321728 is a gapful number since it is divisible by the number (38) 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 31321728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (50122800).

31321728 is an abundant number, since it is smaller than the sum of its proper divisors (68923872).

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

31321728 is an equidigital number, since it uses as much as digits as its factorization.

31321728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101 (or 77 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 31321728 is about 5596.5818139289. The cubic root of 31321728 is about 315.2210693054.

The spelling of 31321728 in words is "thirty-one million, three hundred twenty-one thousand, seven hundred twenty-eight".