28857421 has 2 divisors, whose sum is σ = 28857422. Its totient is φ = 28857420.

The previous prime is 28857419. The next prime is 28857443. The reversal of 28857421 is 12475882.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17222500 + 11634921 = 4150^2 + 3411^2 .

It is a cyclic number.

It is not a de Polignac number, because 28857421 - 2¹ = 28857419 is a prime.

Together with 28857419, it forms a pair of twin primes.

It is equal to p_1791379 and since 28857421 and 1791379 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28857121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14428710 + 14428711.

It is an arithmetic number, because the mean of its divisors is an integer number (14428711).

Almost surely, 2^28857421 is an apocalyptic number.

It is an amenable number.

28857421 is a deficient number, since it is larger than the sum of its proper divisors (1).

28857421 is an equidigital number, since it uses as much as digits as its factorization.

28857421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 35840, while the sum is 37.

The square root of 28857421 is about 5371.9103678301. The cubic root of 28857421 is about 306.7273518583.

The spelling of 28857421 in words is "twenty-eight million, eight hundred fifty-seven thousand, four hundred twenty-one".