21523417 has 2 divisors, whose sum is σ = 21523418. Its totient is φ = 21523416.

The previous prime is 21523399. The next prime is 21523421. The reversal of 21523417 is 71432512.

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., 17438976 + 4084441 = 4176^2 + 2021^2 .

It is a cyclic number.

It is not a de Polignac number, because 21523417 - 2¹¹ = 21521369 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21523391 and 21523400.

It is not a weakly prime, because it can be changed into another prime (21527417) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10761708 + 10761709.

It is an arithmetic number, because the mean of its divisors is an integer number (10761709).

Almost surely, 2^21523417 is an apocalyptic number.

It is an amenable number.

21523417 is a deficient number, since it is larger than the sum of its proper divisors (1).

21523417 is an equidigital number, since it uses as much as digits as its factorization.

21523417 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1680, while the sum is 25.

The square root of 21523417 is about 4639.3336806054. Note that the first 3 decimals coincide. The cubic root of 21523417 is about 278.1658043402.

Adding to 21523417 its reverse (71432512), we get a palindrome (92955929).

It can be divided in two parts, 215 and 23417, that added together give a palindrome (23632).

The spelling of 21523417 in words is "twenty-one million, five hundred twenty-three thousand, four hundred seventeen".