28128631 has 4 divisors (see below), whose sum is σ = 28141192. Its totient is φ = 28116072.

The previous prime is 28128629. The next prime is 28128647. The reversal of 28128631 is 13682182.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 13682182 = 2 ⋅6841091.

It is a cyclic number.

It is not a de Polignac number, because 28128631 - 2¹ = 28128629 is a prime.

It is a super-2 number, since 2×28128631² = 1582439763868322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 28128593 and 28128602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28128671) 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, 1905 + ... + 7738.

It is an arithmetic number, because the mean of its divisors is an integer number (7035298).

Almost surely, 2^28128631 is an apocalyptic number.

28128631 is a deficient number, since it is larger than the sum of its proper divisors (12561).

28128631 is an equidigital number, since it uses as much as digits as its factorization.

28128631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12560.

The product of its digits is 4608, while the sum is 31.

The square root of 28128631 is about 5303.6431818138. The cubic root of 28128631 is about 304.1231863121.

The spelling of 28128631 in words is "twenty-eight million, one hundred twenty-eight thousand, six hundred thirty-one".