28457991 has 24 divisors (see below), whose sum is σ = 43483440. Its totient is φ = 17934480.

The previous prime is 28457971. The next prime is 28457993. The reversal of 28457991 is 19975482.

It is not a de Polignac number, because 28457991 - 2⁹ = 28457479 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28457993) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 61501 + ... + 61961.

It is an arithmetic number, because the mean of its divisors is an integer number (1811810).

Almost surely, 2^28457991 is an apocalyptic number.

28457991 is a deficient number, since it is larger than the sum of its proper divisors (15025449).

28457991 is an equidigital number, since it uses as much as digits as its factorization.

28457991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 524 (or 483 counting only the distinct ones).

The product of its digits is 181440, while the sum is 45.

The square root of 28457991 is about 5334.6031717458. The cubic root of 28457991 is about 305.3055828289.

The spelling of 28457991 in words is "twenty-eight million, four hundred fifty-seven thousand, nine hundred ninety-one".