28971891 has 32 divisors (see below), whose sum is σ = 47040000. Its totient is φ = 17514144.

The previous prime is 28971857. The next prime is 28971923. The reversal of 28971891 is 19817982.

It is not a de Polignac number, because 28971891 - 2¹⁵ = 28939123 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28971991) 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, 20010 + ... + 21408.

It is an arithmetic number, because the mean of its divisors is an integer number (1470000).

Almost surely, 2^28971891 is an apocalyptic number.

28971891 is a deficient number, since it is larger than the sum of its proper divisors (18068109).

28971891 is a wasteful number, since it uses less digits than its factorization.

28971891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1480 (or 1474 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 28971891 is about 5382.5543192800. The cubic root of 28971891 is about 307.1323863952.

The spelling of 28971891 in words is "twenty-eight million, nine hundred seventy-one thousand, eight hundred ninety-one".