21605053 has 2 divisors, whose sum is σ = 21605054. Its totient is φ = 21605052.

The previous prime is 21605039. The next prime is 21605057. The reversal of 21605053 is 35050612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17455684 + 4149369 = 4178^2 + 2037^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21605053 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21605057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10802526 + 10802527.

It is an arithmetic number, because the mean of its divisors is an integer number (10802527).

Almost surely, 2^21605053 is an apocalyptic number.

It is an amenable number.

21605053 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605053 is an equidigital number, since it uses as much as digits as its factorization.

21605053 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 900, while the sum is 22.

The square root of 21605053 is about 4648.1235999057. The cubic root of 21605053 is about 278.5170449424.

Adding to 21605053 its reverse (35050612), we get a palindrome (56655665).

The spelling of 21605053 in words is "twenty-one million, six hundred five thousand, fifty-three".