21717523 has 2 divisors, whose sum is σ = 21717524. Its totient is φ = 21717522.

The previous prime is 21717473. The next prime is 21717539. The reversal of 21717523 is 32571712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21717523 - 2²¹ = 19620371 is a prime.

It is a super-3 number, since 3×21717523³ (a number of 23 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21717491 and 21717500.

It is not a weakly prime, because it can be changed into another prime (21718523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10858761 + 10858762.

It is an arithmetic number, because the mean of its divisors is an integer number (10858762).

Almost surely, 2^21717523 is an apocalyptic number.

21717523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21717523 is an equidigital number, since it uses as much as digits as its factorization.

21717523 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2940, while the sum is 28.

The square root of 21717523 is about 4660.2063259045. The cubic root of 21717523 is about 278.9995032600. Note that the first 3 decimals are identical.

The spelling of 21717523 in words is "twenty-one million, seven hundred seventeen thousand, five hundred twenty-three".