28887991 has 4 divisors (see below), whose sum is σ = 31514184. Its totient is φ = 26261800.

The previous prime is 28887979. The next prime is 28888003. The reversal of 28887991 is 19978882.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (28887979) and next prime (28888003).

It is a cyclic number.

It is not a de Polignac number, because 28887991 - 2⁷ = 28887863 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28887941) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1313080 + ... + 1313101.

It is an arithmetic number, because the mean of its divisors is an integer number (7878546).

Almost surely, 2^28887991 is an apocalyptic number.

28887991 is a deficient number, since it is larger than the sum of its proper divisors (2626193).

28887991 is a wasteful number, since it uses less digits than its factorization.

28887991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2626192.

The product of its digits is 580608, while the sum is 52.

The square root of 28887991 is about 5374.7549711592. The cubic root of 28887991 is about 306.8356237889.

The spelling of 28887991 in words is "twenty-eight million, eight hundred eighty-seven thousand, nine hundred ninety-one".