21342421 has 2 divisors, whose sum is σ = 21342422. Its totient is φ = 21342420.

The previous prime is 21342407. The next prime is 21342437. The reversal of 21342421 is 12424312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16719921 + 4622500 = 4089^2 + 2150^2 .

It is a cyclic number.

It is not a de Polignac number, because 21342421 - 2¹¹ = 21340373 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21342481) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10671210 + 10671211.

It is an arithmetic number, because the mean of its divisors is an integer number (10671211).

Almost surely, 2^21342421 is an apocalyptic number.

It is an amenable number.

21342421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21342421 is an equidigital number, since it uses as much as digits as its factorization.

21342421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 384, while the sum is 19.

The square root of 21342421 is about 4619.7858175461. The cubic root of 21342421 is about 277.3838856255.

Adding to 21342421 its reverse (12424312), we get a palindrome (33766733).

The spelling of 21342421 in words is "twenty-one million, three hundred forty-two thousand, four hundred twenty-one".