28215540 has 60 divisors (see below), whose sum is σ = 88518276. Its totient is φ = 7523712.

The previous prime is 28215527. The next prime is 28215541. The reversal of 28215540 is 4551282.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 19607184 + 8608356 = 4428^2 + 2934^2 .

It is a tau number, because it is divible by the number of its divisors (60).

It is a super-2 number, since 2×28215540² = 1592233394983200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28215541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 7089 + ... + 10328.

Almost surely, 2^28215540 is an apocalyptic number.

28215540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28215540 is an abundant number, since it is smaller than the sum of its proper divisors (60302736).

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

28215540 is a wasteful number, since it uses less digits than its factorization.

28215540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17438 (or 17427 counting only the distinct ones).

The product of its (nonzero) digits is 3200, while the sum is 27.

The square root of 28215540 is about 5311.8301930691. The cubic root of 28215540 is about 304.4360806404.

It can be divided in two parts, 282 and 15540, that multiplied together give a triangular number (4382280 = T₂₉₆₀).

The spelling of 28215540 in words is "twenty-eight million, two hundred fifteen thousand, five hundred forty".