28431157 has 4 divisors (see below), whose sum is σ = 30103596. Its totient is φ = 26758720.

The previous prime is 28431113. The next prime is 28431167. The reversal of 28431157 is 75113482.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 75113482 = 2 ⋅37556741.

It can be written as a sum of positive squares in 2 ways, for example, as 11464996 + 16966161 = 3386^2 + 4119^2 .

It is a cyclic number.

It is not a de Polignac number, because 28431157 - 2¹¹ = 28429109 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28431167) 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, 836194 + ... + 836227.

It is an arithmetic number, because the mean of its divisors is an integer number (7525899).

Almost surely, 2^28431157 is an apocalyptic number.

It is an amenable number.

28431157 is a deficient number, since it is larger than the sum of its proper divisors (1672439).

28431157 is a wasteful number, since it uses less digits than its factorization.

28431157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1672438.

The product of its digits is 6720, while the sum is 31.

The square root of 28431157 is about 5332.0874899049. The cubic root of 28431157 is about 305.2095916727.

The spelling of 28431157 in words is "twenty-eight million, four hundred thirty-one thousand, one hundred fifty-seven".