21425021 has 2 divisors, whose sum is σ = 21425022. Its totient is φ = 21425020.

The previous prime is 21425009. The next prime is 21425023. The reversal of 21425021 is 12052412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17757796 + 3667225 = 4214^2 + 1915^2 .

It is a cyclic number.

It is not a de Polignac number, because 21425021 - 2⁶ = 21424957 is a prime.

Together with 21425023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21425023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10712510 + 10712511.

It is an arithmetic number, because the mean of its divisors is an integer number (10712511).

Almost surely, 2^21425021 is an apocalyptic number.

It is an amenable number.

21425021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21425021 is an equidigital number, since it uses as much as digits as its factorization.

21425021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 160, while the sum is 17.

The square root of 21425021 is about 4628.7169928610. The cubic root of 21425021 is about 277.7412711075.

Adding to 21425021 its reverse (12052412), we get a palindrome (33477433).

The spelling of 21425021 in words is "twenty-one million, four hundred twenty-five thousand, twenty-one".