28171409 has 4 divisors (see below), whose sum is σ = 32195904. Its totient is φ = 24146916.

The previous prime is 28171399. The next prime is 28171411. The reversal of 28171409 is 90417182.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 90417182 = 2 ⋅45208591.

It is a cyclic number.

It is not a de Polignac number, because 28171409 - 2⁸ = 28171153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28171009) 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, 2012237 + ... + 2012250.

It is an arithmetic number, because the mean of its divisors is an integer number (8048976).

Almost surely, 2^28171409 is an apocalyptic number.

It is an amenable number.

28171409 is a deficient number, since it is larger than the sum of its proper divisors (4024495).

28171409 is an equidigital number, since it uses as much as digits as its factorization.

28171409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4024494.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 28171409 is about 5307.6745378744. The cubic root of 28171409 is about 304.2772783253.

It can be divided in two parts, 2817 and 1409, that multiplied together give a triangular number (3969153 = T₂₈₁₇).

The spelling of 28171409 in words is "twenty-eight million, one hundred seventy-one thousand, four hundred nine".