21345123 has 4 divisors (see below), whose sum is σ = 28460168. Its totient is φ = 14230080.

The previous prime is 21345119. The next prime is 21345187. The reversal of 21345123 is 32154312.

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

It is not a de Polignac number, because 21345123 - 2² = 21345119 is a prime.

It is a super-2 number, since 2×21345123² = 911228551770258, which contains 22 as substring.

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 21345123.

It is not an unprimeable number, because it can be changed into a prime (21345223) 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 3 ways as a sum of consecutive naturals, for example, 3557518 + ... + 3557523.

It is an arithmetic number, because the mean of its divisors is an integer number (7115042).

Almost surely, 2^21345123 is an apocalyptic number.

21345123 is a deficient number, since it is larger than the sum of its proper divisors (7115045).

21345123 is an equidigital number, since it uses as much as digits as its factorization.

21345123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7115044.

The product of its digits is 720, while the sum is 21.

The square root of 21345123 is about 4620.0782460906. The cubic root of 21345123 is about 277.3955909460.

Adding to 21345123 its reverse (32154312), we get a palindrome (53499435).

The spelling of 21345123 in words is "twenty-one million, three hundred forty-five thousand, one hundred twenty-three".