28726181991 has 12 divisors (see below), whose sum is σ = 44685172168. Its totient is φ = 17677650384.

The previous prime is 28726181933. The next prime is 28726181993. The reversal of 28726181991 is 19918162782.

It is a happy number.

28726181991 is a `hidden beast` number, since 2 + 8 + 7 + 2 + 618 + 19 + 9 + 1 = 666.

It is not a de Polignac number, because 28726181991 - 2¹³ = 28726173799 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28726181993) 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, 122761345 + ... + 122761578.

Almost surely, 2^28726181991 is an apocalyptic number.

28726181991 is a deficient number, since it is larger than the sum of its proper divisors (15958990177).

28726181991 is a wasteful number, since it uses less digits than its factorization.

28726181991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 245522942 (or 245522939 counting only the distinct ones).

The product of its digits is 870912, while the sum is 54.

The spelling of 28726181991 in words is "twenty-eight billion, seven hundred twenty-six million, one hundred eighty-one thousand, nine hundred ninety-one".