21338521 has 2 divisors, whose sum is σ = 21338522. Its totient is φ = 21338520.

The previous prime is 21338507. The next prime is 21338531. The reversal of 21338521 is 12583312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21206025 + 132496 = 4605^2 + 364^2 .

It is a cyclic number.

It is not a de Polignac number, because 21338521 - 2¹¹ = 21336473 is a prime.

It is a plaindrome in base 16.

It is not a weakly prime, because it can be changed into another prime (21338531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10669260 + 10669261.

It is an arithmetic number, because the mean of its divisors is an integer number (10669261).

Almost surely, 2^21338521 is an apocalyptic number.

It is an amenable number.

21338521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21338521 is an equidigital number, since it uses as much as digits as its factorization.

21338521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1440, while the sum is 25.

The square root of 21338521 is about 4619.3637007709. The cubic root of 21338521 is about 277.3669887131.

The spelling of 21338521 in words is "twenty-one million, three hundred thirty-eight thousand, five hundred twenty-one".