21202121123 has 4 divisors (see below), whose sum is σ = 21518570760. Its totient is φ = 20885671488.

The previous prime is 21202121111. The next prime is 21202121173. The reversal of 21202121123 is 32112120212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21202121123 is a prime.

It is a super-2 number, since 2×21202121123² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21202121173) 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, 158224718 + ... + 158224851.

It is an arithmetic number, because the mean of its divisors is an integer number (5379642690).

Almost surely, 2^21202121123 is an apocalyptic number.

21202121123 is a deficient number, since it is larger than the sum of its proper divisors (316449637).

21202121123 is an equidigital number, since it uses as much as digits as its factorization.

21202121123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316449636.

The product of its (nonzero) digits is 96, while the sum is 17.

Adding to 21202121123 its reverse (32112120212), we get a palindrome (53314241335).

The spelling of 21202121123 in words is "twenty-one billion, two hundred two million, one hundred twenty-one thousand, one hundred twenty-three".