28191920 has 20 divisors (see below), whose sum is σ = 65546400. Its totient is φ = 11276736.

The previous prime is 28191893. The next prime is 28191923. The reversal of 28191920 is 2919182.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (28191923) 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, 176120 + ... + 176279.

It is an arithmetic number, because the mean of its divisors is an integer number (3277320).

Almost surely, 2^28191920 is an apocalyptic number.

28191920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28191920 is an abundant number, since it is smaller than the sum of its proper divisors (37354480).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28191920 is a wasteful number, since it uses less digits than its factorization.

28191920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352412 (or 352406 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 28191920 is about 5309.6063884247. The cubic root of 28191920 is about 304.3511063355.

The spelling of 28191920 in words is "twenty-eight million, one hundred ninety-one thousand, nine hundred twenty".