28457721 has 12 divisors (see below), whose sum is σ = 42432000. Its totient is φ = 18359640.

The previous prime is 28457719. The next prime is 28457743. The reversal of 28457721 is 12775482.

28457721 is a `hidden beast` number, since 2 + 84 + 577 + 2 + 1 = 666.

It is not a de Polignac number, because 28457721 - 2¹ = 28457719 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (28457771) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 50721 + ... + 51278.

It is an arithmetic number, because the mean of its divisors is an integer number (3536000).

Almost surely, 2^28457721 is an apocalyptic number.

It is an amenable number.

28457721 is a deficient number, since it is larger than the sum of its proper divisors (13974279).

28457721 is a wasteful number, since it uses less digits than its factorization.

28457721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102036 (or 102033 counting only the distinct ones).

The product of its digits is 31360, while the sum is 36.

The square root of 28457721 is about 5334.5778652111. The cubic root of 28457721 is about 305.3046172797.

The spelling of 28457721 in words is "twenty-eight million, four hundred fifty-seven thousand, seven hundred twenty-one".