28134157921 has 4 divisors (see below), whose sum is σ = 28135002132. Its totient is φ = 28133313712.

The previous prime is 28134157897. The next prime is 28134157967. The reversal of 28134157921 is 12975143182.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12975143182 = 2 ⋅6487571591.

It can be written as a sum of positive squares in 2 ways, for example, as 11186023696 + 16948134225 = 105764^2 + 130185^2 .

It is a cyclic number.

It is not a de Polignac number, because 28134157921 - 2²⁹ = 27597287009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28134157621) 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, 369970 + ... + 439483.

It is an arithmetic number, because the mean of its divisors is an integer number (7033750533).

Almost surely, 2^28134157921 is an apocalyptic number.

It is an amenable number.

28134157921 is a deficient number, since it is larger than the sum of its proper divisors (844211).

28134157921 is an equidigital number, since it uses as much as digits as its factorization.

28134157921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 844210.

The product of its digits is 120960, while the sum is 43.

The spelling of 28134157921 in words is "twenty-eight billion, one hundred thirty-four million, one hundred fifty-seven thousand, nine hundred twenty-one".