28531720 has 48 divisors (see below), whose sum is σ = 74682540. Its totient is φ = 9781632.

The previous prime is 28531717. The next prime is 28531733. The reversal of 28531720 is 2713582.

It can be written as a sum of positive squares in 2 ways, for example, as 26687556 + 1844164 = 5166^2 + 1358^2 .

It is a super-3 number, since 3×28531720³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 5319 + ... + 9238.

Almost surely, 2^28531720 is an apocalyptic number.

28531720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28531720 is an abundant number, since it is smaller than the sum of its proper divisors (46150820).

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

28531720 is a wasteful number, since it uses less digits than its factorization.

28531720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14582 (or 14571 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 28531720 is about 5341.5091500436. The cubic root of 28531720 is about 305.5690174908.

The spelling of 28531720 in words is "twenty-eight million, five hundred thirty-one thousand, seven hundred twenty".