28509987 has 32 divisors (see below), whose sum is σ = 44328960. Its totient is φ = 16144800.

The previous prime is 28509983. The next prime is 28509991. The reversal of 28509987 is 78990582.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (28509983) and next prime (28509991).

It is not a de Polignac number, because 28509987 - 2² = 28509983 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28509983) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 919662 + ... + 919692.

It is an arithmetic number, because the mean of its divisors is an integer number (1385280).

Almost surely, 2^28509987 is an apocalyptic number.

28509987 is a deficient number, since it is larger than the sum of its proper divisors (15818973).

28509987 is an equidigital number, since it uses as much as digits as its factorization.

28509987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136 (or 74 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 48.

The square root of 28509987 is about 5339.4744123369. The cubic root of 28509987 is about 305.4914124213.

It can be divided in two parts, 28 and 509987, that added together give a palindrome (510015).

The spelling of 28509987 in words is "twenty-eight million, five hundred nine thousand, nine hundred eighty-seven".