21203111021 has 4 divisors (see below), whose sum is σ = 21241874112. Its totient is φ = 21164347932.

The previous prime is 21203111003. The next prime is 21203111029. The reversal of 21203111021 is 12011130212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21203111021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21203110987 and 21203111005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21203111029) 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, 19380725 + ... + 19381818.

It is an arithmetic number, because the mean of its divisors is an integer number (5310468528).

Almost surely, 2^21203111021 is an apocalyptic number.

It is an amenable number.

21203111021 is a deficient number, since it is larger than the sum of its proper divisors (38763091).

21203111021 is an equidigital number, since it uses as much as digits as its factorization.

21203111021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38763090.

The product of its (nonzero) digits is 24, while the sum is 14.

Adding to 21203111021 its reverse (12011130212), we get a palindrome (33214241233).

The spelling of 21203111021 in words is "twenty-one billion, two hundred three million, one hundred eleven thousand, twenty-one".