28172091 has 4 divisors (see below), whose sum is σ = 37562792. Its totient is φ = 18781392.

The previous prime is 28172069. The next prime is 28172147. The reversal of 28172091 is 19027182.

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

It is not a de Polignac number, because 28172091 - 2¹⁴ = 28155707 is a prime.

It is a super-2 number, since 2×28172091² = 1587333422624562, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28172051) 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, 4695346 + ... + 4695351.

It is an arithmetic number, because the mean of its divisors is an integer number (9390698).

Almost surely, 2^28172091 is an apocalyptic number.

28172091 is a deficient number, since it is larger than the sum of its proper divisors (9390701).

28172091 is an equidigital number, since it uses as much as digits as its factorization.

28172091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9390700.

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 28172091 is about 5307.7387840775. The cubic root of 28172091 is about 304.2797337158.

The spelling of 28172091 in words is "twenty-eight million, one hundred seventy-two thousand, ninety-one".