28931557 has 2 divisors, whose sum is σ = 28931558. Its totient is φ = 28931556.

The previous prime is 28931549. The next prime is 28931593. The reversal of 28931557 is 75513982.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 24117921 + 4813636 = 4911^2 + 2194^2 .

It is a cyclic number.

It is not a de Polignac number, because 28931557 - 2³ = 28931549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28931537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14465778 + 14465779.

It is an arithmetic number, because the mean of its divisors is an integer number (14465779).

Almost surely, 2^28931557 is an apocalyptic number.

It is an amenable number.

28931557 is a deficient number, since it is larger than the sum of its proper divisors (1).

28931557 is an equidigital number, since it uses as much as digits as its factorization.

28931557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 75600, while the sum is 40.

The square root of 28931557 is about 5378.8062802075. The cubic root of 28931557 is about 306.9897926558.

The spelling of 28931557 in words is "twenty-eight million, nine hundred thirty-one thousand, five hundred fifty-seven".