28761891991 has 24 divisors (see below), whose sum is σ = 35888188320. Its totient is φ = 22550101056.

The previous prime is 28761891973. The next prime is 28761892009. The reversal of 28761891991 is 19919816782.

It is an interprime number because it is at equal distance from previous prime (28761891973) and next prime (28761892009).

It is not a de Polignac number, because 28761891991 - 2⁵ = 28761891959 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 (28761891911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 122956 + ... + 269521.

It is an arithmetic number, because the mean of its divisors is an integer number (1495341180).

Almost surely, 2^28761891991 is an apocalyptic number.

28761891991 is a deficient number, since it is larger than the sum of its proper divisors (7126296329).

28761891991 is a wasteful number, since it uses less digits than its factorization.

28761891991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 392551 (or 392532 counting only the distinct ones).

The product of its digits is 3919104, while the sum is 61.

The spelling of 28761891991 in words is "twenty-eight billion, seven hundred sixty-one million, eight hundred ninety-one thousand, nine hundred ninety-one".