28531840 has 64 divisors (see below), whose sum is σ = 69003000. Its totient is φ = 11280384.

The previous prime is 28531837. The next prime is 28531843. The reversal of 28531840 is 4813582.

It is an interprime number because it is at equal distance from previous prime (28531837) and next prime (28531843).

It can be written as a sum of positive squares in 4 ways, for example, as 28132416 + 399424 = 5304^2 + 632^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28531843) 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 7 ways as a sum of consecutive naturals, for example, 69556 + ... + 69964.

Almost surely, 2^28531840 is an apocalyptic number.

28531840 is a gapful number since it is divisible by the number (20) 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 28531840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34501500).

28531840 is an abundant number, since it is smaller than the sum of its proper divisors (40471160).

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

28531840 is a wasteful number, since it uses less digits than its factorization.

28531840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 537 (or 525 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 31.

The square root of 28531840 is about 5341.5203828124. The cubic root of 28531840 is about 305.5694458822.

The spelling of 28531840 in words is "twenty-eight million, five hundred thirty-one thousand, eight hundred forty".