21719123 has 4 divisors (see below), whose sum is σ = 22181280. Its totient is φ = 21256968.

The previous prime is 21719099. The next prime is 21719129. The reversal of 21719123 is 32191712.

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 21719123 - 2¹⁸ = 21456979 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21719092 and 21719101.

It is not an unprimeable number, because it can be changed into a prime (21719129) 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, 231008 + ... + 231101.

It is an arithmetic number, because the mean of its divisors is an integer number (5545320).

Almost surely, 2^21719123 is an apocalyptic number.

21719123 is a deficient number, since it is larger than the sum of its proper divisors (462157).

21719123 is an equidigital number, since it uses as much as digits as its factorization.

21719123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 462156.

The product of its digits is 756, while the sum is 26.

The square root of 21719123 is about 4660.3779889618. The cubic root of 21719123 is about 279.0063546897.

The spelling of 21719123 in words is "twenty-one million, seven hundred nineteen thousand, one hundred twenty-three".