28131251721 has 16 divisors (see below), whose sum is σ = 40365773568. Its totient is φ = 17361619200.

The previous prime is 28131251719. The next prime is 28131251773. The reversal of 28131251721 is 12715213182.

It is not a de Polignac number, because 28131251721 - 2¹ = 28131251719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28131251791) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4518145 + ... + 4524366.

It is an arithmetic number, because the mean of its divisors is an integer number (2522860848).

Almost surely, 2^28131251721 is an apocalyptic number.

It is an amenable number.

28131251721 is a deficient number, since it is larger than the sum of its proper divisors (12234521847).

28131251721 is a wasteful number, since it uses less digits than its factorization.

28131251721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9042592.

The product of its digits is 6720, while the sum is 33.

The spelling of 28131251721 in words is "twenty-eight billion, one hundred thirty-one million, two hundred fifty-one thousand, seven hundred twenty-one".