21250121 has 2 divisors, whose sum is σ = 21250122. Its totient is φ = 21250120.

The previous prime is 21250111. The next prime is 21250123. The reversal of 21250121 is 12105212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18800896 + 2449225 = 4336^2 + 1565^2 .

It is a cyclic number.

It is not a de Polignac number, because 21250121 - 2⁶ = 21250057 is a prime.

Together with 21250123, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21250096 and 21250105.

It is not a weakly prime, because it can be changed into another prime (21250123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10625060 + 10625061.

It is an arithmetic number, because the mean of its divisors is an integer number (10625061).

Almost surely, 2^21250121 is an apocalyptic number.

It is an amenable number.

21250121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21250121 is an equidigital number, since it uses as much as digits as its factorization.

21250121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21250121 is about 4609.7853529205. The cubic root of 21250121 is about 276.9834385612.

Adding to 21250121 its reverse (12105212), we get a palindrome (33355333).

The spelling of 21250121 in words is "twenty-one million, two hundred fifty thousand, one hundred twenty-one".