21201421 has 2 divisors, whose sum is σ = 21201422. Its totient is φ = 21201420.

The previous prime is 21201419. The next prime is 21201443. The reversal of 21201421 is 12410212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19272100 + 1929321 = 4390^2 + 1389^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201421 - 2¹ = 21201419 is a prime.

Together with 21201419, it forms a pair of twin primes.

It is the 4605-th Hogben number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201461) by changing a digit.

It is a nontrivial repunit in base 4604.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600710 + 10600711.

It is an arithmetic number, because the mean of its divisors is an integer number (10600711).

Almost surely, 2^21201421 is an apocalyptic number.

It is an amenable number.

21201421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201421 is an equidigital number, since it uses as much as digits as its factorization.

21201421 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21201421 is about 4604.5000814421. The cubic root of 21201421 is about 276.7716842979.

Adding to 21201421 its reverse (12410212), we get a palindrome (33611633).

The spelling of 21201421 in words is "twenty-one million, two hundred one thousand, four hundred twenty-one".