21042123 has 16 divisors (see below), whose sum is σ = 28538400. Its totient is φ = 13789440.

The previous prime is 21042103. The next prime is 21042127. The reversal of 21042123 is 32124012.

It is not a de Polignac number, because 21042123 - 2⁶ = 21042059 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21042127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 74743 + ... + 75023.

It is an arithmetic number, because the mean of its divisors is an integer number (1783650).

Almost surely, 2^21042123 is an apocalyptic number.

21042123 is a deficient number, since it is larger than the sum of its proper divisors (7496277).

21042123 is a wasteful number, since it uses less digits than its factorization.

21042123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 622.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21042123 is about 4587.1693886317. The cubic root of 21042123 is about 276.0767613628.

Adding to 21042123 its reverse (32124012), we get a palindrome (53166135).

The spelling of 21042123 in words is "twenty-one million, forty-two thousand, one hundred twenty-three".