21001121 has 2 divisors, whose sum is σ = 21001122.
Its totient is φ = 21001120.
The previous prime is 21001117. The next prime is 21001153. The reversal of 21001121 is 12110012.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 19140625 + 1860496 = 4375^2 + 1364^2
It is a cyclic number.
It is not a de Polignac number, because 21001121 - 22 = 21001117 is a prime.
It is a junction number, because it is equal to n+sod(n) for n = 21001099 and 21001108.
It is not a weakly prime, because it can be changed into another prime (21001181) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500560 + 10500561.
It is an arithmetic number, because the mean of its divisors is an integer number (10500561).
Almost surely, 221001121 is an apocalyptic number.
It is an amenable number.
21001121 is a deficient number, since it is larger than the sum of its proper divisors (1).
21001121 is an equidigital number, since it uses as much as digits as its factorization.
21001121 is an evil number, because the sum of its binary digits is even.
The product of its (nonzero) digits is 4, while the sum is 8.
The square root of 21001121 is about 4582.6980044511.
The cubic root of 21001121 is about 275.8973266841.
Adding to 21001121 its reverse (12110012), we get a palindrome (33111133).
The spelling of 21001121 in words is "twenty-one million, one thousand, one hundred twenty-one".