21713123 has 4 divisors (see below), whose sum is σ = 21782808. Its totient is φ = 21643440.

The previous prime is 21713099. The next prime is 21713129. The reversal of 21713123 is 32131712.

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 21713123 - 2⁶ = 21713059 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21713095 and 21713104.

It is not an unprimeable number, because it can be changed into a prime (21713129) 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, 34373 + ... + 34998.

It is an arithmetic number, because the mean of its divisors is an integer number (5445702).

Almost surely, 2^21713123 is an apocalyptic number.

21713123 is a deficient number, since it is larger than the sum of its proper divisors (69685).

21713123 is an equidigital number, since it uses as much as digits as its factorization.

21713123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69684.

The product of its digits is 252, while the sum is 20.

The square root of 21713123 is about 4659.7342198885. The cubic root of 21713123 is about 278.9806600932.

Adding to 21713123 its reverse (32131712), we get a palindrome (53844835).

It can be divided in two parts, 217 and 13123, that multiplied together give a triangular number (2847691 = T₂₃₈₆).

The spelling of 21713123 in words is "twenty-one million, seven hundred thirteen thousand, one hundred twenty-three".