28457921 has 8 divisors (see below), whose sum is σ = 29361384. Its totient is φ = 27561600.

The previous prime is 28457917. The next prime is 28457929. The reversal of 28457921 is 12975482.

It can be written as a sum of positive squares in 4 ways, for example, as 2560000 + 25897921 = 1600^2 + 5089^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 28457921 - 2² = 28457917 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28457929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6971 + ... + 10271.

It is an arithmetic number, because the mean of its divisors is an integer number (3670173).

Almost surely, 2^28457921 is an apocalyptic number.

It is an amenable number.

28457921 is a deficient number, since it is larger than the sum of its proper divisors (903463).

28457921 is a wasteful number, since it uses less digits than its factorization.

28457921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3571.

The product of its digits is 40320, while the sum is 38.

The square root of 28457921 is about 5334.5966108039. The cubic root of 28457921 is about 305.3053325019.

The spelling of 28457921 in words is "twenty-eight million, four hundred fifty-seven thousand, nine hundred twenty-one".