21508241 has 2 divisors, whose sum is σ = 21508242. Its totient is φ = 21508240.

The previous prime is 21508237. The next prime is 21508259. The reversal of 21508241 is 14280512.

21508241 is nontrivially palindromic in base 8.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17977600 + 3530641 = 4240^2 + 1879^2 .

It is a cyclic number.

It is not a de Polignac number, because 21508241 - 2² = 21508237 is a prime.

It is not a weakly prime, because it can be changed into another prime (21508261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10754120 + 10754121.

It is an arithmetic number, because the mean of its divisors is an integer number (10754121).

Almost surely, 2^21508241 is an apocalyptic number.

It is an amenable number.

21508241 is a deficient number, since it is larger than the sum of its proper divisors (1).

21508241 is an equidigital number, since it uses as much as digits as its factorization.

21508241 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 21508241 is about 4637.6978124927. The cubic root of 21508241 is about 278.1004114272.

Adding to 21508241 its reverse (14280512), we get a palindrome (35788753).

The spelling of 21508241 in words is "twenty-one million, five hundred eight thousand, two hundred forty-one".