28251997 has 4 divisors (see below), whose sum is σ = 28290076. Its totient is φ = 28213920.

The previous prime is 28251961. The next prime is 28252009. The reversal of 28251997 is 79915282.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20738916 + 7513081 = 4554^2 + 2741^2 .

It is a cyclic number.

It is not a de Polignac number, because 28251997 - 2¹⁹ = 27727709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28251907) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17904 + ... + 19417.

It is an arithmetic number, because the mean of its divisors is an integer number (7072519).

Almost surely, 2^28251997 is an apocalyptic number.

It is an amenable number.

28251997 is a deficient number, since it is larger than the sum of its proper divisors (38079).

28251997 is an equidigital number, since it uses as much as digits as its factorization.

28251997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38078.

The product of its digits is 90720, while the sum is 43.

The square root of 28251997 is about 5315.2607650049. The cubic root of 28251997 is about 304.5671437519.

The spelling of 28251997 in words is "twenty-eight million, two hundred fifty-one thousand, nine hundred ninety-seven".