21928187 has 4 divisors (see below), whose sum is σ = 21946320. Its totient is φ = 21910056.

The previous prime is 21928171. The next prime is 21928189. The reversal of 21928187 is 78182912.

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

It is a cyclic number.

It is not a de Polignac number, because 21928187 - 2⁴ = 21928171 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21928187.

It is not an unprimeable number, because it can be changed into a prime (21928189) 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, 7112 + ... + 9717.

It is an arithmetic number, because the mean of its divisors is an integer number (5486580).

Almost surely, 2^21928187 is an apocalyptic number.

21928187 is a deficient number, since it is larger than the sum of its proper divisors (18133).

21928187 is a wasteful number, since it uses less digits than its factorization.

21928187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18132.

The product of its digits is 16128, while the sum is 38.

The square root of 21928187 is about 4682.7542109319. The cubic root of 21928187 is about 279.8987176200.

The spelling of 21928187 in words is "twenty-one million, nine hundred twenty-eight thousand, one hundred eighty-seven".