28721987 has 12 divisors (see below), whose sum is σ = 33659640. Its totient is φ = 24435936.

The previous prime is 28721983. The next prime is 28721989. The reversal of 28721987 is 78912782.

It is not a de Polignac number, because 28721987 - 2² = 28721983 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28721981) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4703 + ... + 8919.

It is an arithmetic number, because the mean of its divisors is an integer number (2804970).

Almost surely, 2^28721987 is an apocalyptic number.

28721987 is a deficient number, since it is larger than the sum of its proper divisors (4937653).

28721987 is a wasteful number, since it uses less digits than its factorization.

28721987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4370 (or 4363 counting only the distinct ones).

The product of its digits is 112896, while the sum is 44.

The square root of 28721987 is about 5359.2897850368. The cubic root of 28721987 is about 306.2467537071.

The spelling of 28721987 in words is "twenty-eight million, seven hundred twenty-one thousand, nine hundred eighty-seven".