21200042123 has 4 divisors (see below), whose sum is σ = 22830814608. Its totient is φ = 19569269640.

The previous prime is 21200042111. The next prime is 21200042161. The reversal of 21200042123 is 32124000212.

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 21200042123 - 2⁸ = 21200041867 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21200042023) 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, 815386223 + ... + 815386248.

It is an arithmetic number, because the mean of its divisors is an integer number (5707703652).

Almost surely, 2^21200042123 is an apocalyptic number.

21200042123 is a deficient number, since it is larger than the sum of its proper divisors (1630772485).

21200042123 is a wasteful number, since it uses less digits than its factorization.

21200042123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1630772484.

The product of its (nonzero) digits is 192, while the sum is 17.

Adding to 21200042123 its reverse (32124000212), we get a palindrome (53324042335).

The spelling of 21200042123 in words is "twenty-one billion, two hundred million, forty-two thousand, one hundred twenty-three".