31123728 has 90 divisors (see below), whose sum is σ = 90561354. Its totient is φ = 9977856.

The previous prime is 31123727. The next prime is 31123789. The reversal of 31123728 is 82732113.

31123728 = 212² + 213² + ... + 468².

It can be written as a sum of positive squares in 3 ways, for example, as 14379264 + 16744464 = 3792^2 + 4092^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31123723) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 120976 + ... + 121232.

Almost surely, 2^31123728 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 31123728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45280677).

31123728 is an abundant number, since it is smaller than the sum of its proper divisors (59437626).

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

31123728 is a wasteful number, since it uses less digits than its factorization.

31123728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329 (or 291 counting only the distinct ones).

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

The square root of 31123728 is about 5578.8644005747. The cubic root of 31123728 is about 314.5554424327. Note that the first 3 decimals are identical.

The spelling of 31123728 in words is "thirty-one million, one hundred twenty-three thousand, seven hundred twenty-eight".