21256109 has 8 divisors (see below), whose sum is σ = 24350400. Its totient is φ = 18176256.

The previous prime is 21256099. The next prime is 21256129. The reversal of 21256109 is 90165212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21256109 - 2⁸ = 21255853 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 239 + ... + 6524.

It is an arithmetic number, because the mean of its divisors is an integer number (3043800).

Almost surely, 2^21256109 is an apocalyptic number.

It is an amenable number.

21256109 is a deficient number, since it is larger than the sum of its proper divisors (3094291).

21256109 is an equidigital number, since it uses as much as digits as its factorization.

21256109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7219.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 21256109 is about 4610.4347951142. The cubic root of 21256109 is about 277.0094528611.

The spelling of 21256109 in words is "twenty-one million, two hundred fifty-six thousand, one hundred nine".