28021987 has 8 divisors (see below), whose sum is σ = 32890976. Its totient is φ = 23369472.

The previous prime is 28021969. The next prime is 28021993. The reversal of 28021987 is 78912082.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 28021987 - 2¹⁹ = 27497699 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28021907) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 53838 + ... + 54355.

It is an arithmetic number, because the mean of its divisors is an integer number (4111372).

Almost surely, 2^28021987 is an apocalyptic number.

28021987 is a deficient number, since it is larger than the sum of its proper divisors (4868989).

28021987 is a wasteful number, since it uses less digits than its factorization.

28021987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108237.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 28021987 is about 5293.5797906521. The cubic root of 28021987 is about 303.7383591084.

The spelling of 28021987 in words is "twenty-eight million, twenty-one thousand, nine hundred eighty-seven".