21420121 has 2 divisors, whose sum is σ = 21420122. Its totient is φ = 21420120.

The previous prime is 21420103. The next prime is 21420131. The reversal of 21420121 is 12102412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16491721 + 4928400 = 4061^2 + 2220^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21420121 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21420131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710060 + 10710061.

It is an arithmetic number, because the mean of its divisors is an integer number (10710061).

Almost surely, 2^21420121 is an apocalyptic number.

It is an amenable number.

21420121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21420121 is an equidigital number, since it uses as much as digits as its factorization.

21420121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21420121 is about 4628.1876582524. The cubic root of 21420121 is about 277.7200959281.

Adding to 21420121 its reverse (12102412), we get a palindrome (33522533).

The spelling of 21420121 in words is "twenty-one million, four hundred twenty thousand, one hundred twenty-one".