21124923 has 4 divisors (see below), whose sum is σ = 28166568. Its totient is φ = 14083280.

The previous prime is 21124877. The next prime is 21124927. The reversal of 21124923 is 32942112.

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 21124923 - 2¹⁰ = 21123899 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21124893 and 21124902.

It is not an unprimeable number, because it can be changed into a prime (21124927) 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, 3520818 + ... + 3520823.

It is an arithmetic number, because the mean of its divisors is an integer number (7041642).

Almost surely, 2^21124923 is an apocalyptic number.

21124923 is a deficient number, since it is larger than the sum of its proper divisors (7041645).

21124923 is an equidigital number, since it uses as much as digits as its factorization.

21124923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7041644.

The product of its digits is 864, while the sum is 24.

The square root of 21124923 is about 4596.1857012092. The cubic root of 21124923 is about 276.4384048132.

The spelling of 21124923 in words is "twenty-one million, one hundred twenty-four thousand, nine hundred twenty-three".