31078728 has 84 divisors (see below), whose sum is σ = 88582185. Its totient is φ = 10217664.

The previous prime is 31078717. The next prime is 31078739. The reversal of 31078728 is 82787013.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It is an interprime number because it is at equal distance from previous prime (31078717) and next prime (31078739).

It can be written as a sum of positive squares in 2 ways, for example, as 30935844 + 142884 = 5562^2 + 378^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=3942.

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 = 31078692 and 31078701.

It is an unprimeable number.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 425700 + ... + 425772.

Almost surely, 2^31078728 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 31078728

31078728 is an abundant number, since it is smaller than the sum of its proper divisors (57503457).

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

31078728 is an frugal number, since it uses more digits than its factorization.

31078728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170 (or 78 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

The square root of 31078728 is about 5574.8298628747. The cubic root of 31078728 is about 314.4037701314.

The spelling of 31078728 in words is "thirty-one million, seventy-eight thousand, seven hundred twenty-eight".