21203121 has 4 divisors (see below), whose sum is σ = 28270832. Its totient is φ = 14135412.

The previous prime is 21203113. The next prime is 21203123. The reversal of 21203121 is 12130212.

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 not a de Polignac number, because 21203121 - 2³ = 21203113 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21203097 and 21203106.

It is not an unprimeable number, because it can be changed into a prime (21203123) 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, 3533851 + ... + 3533856.

It is an arithmetic number, because the mean of its divisors is an integer number (7067708).

Almost surely, 2^21203121 is an apocalyptic number.

It is an amenable number.

21203121 is a deficient number, since it is larger than the sum of its proper divisors (7067711).

21203121 is an equidigital number, since it uses as much as digits as its factorization.

21203121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7067710.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21203121 is about 4604.6846797582. The cubic root of 21203121 is about 276.7790815896.

Adding to 21203121 its reverse (12130212), we get a palindrome (33333333).

The spelling of 21203121 in words is "twenty-one million, two hundred three thousand, one hundred twenty-one".