21008573 has 2 divisors, whose sum is σ = 21008574. Its totient is φ = 21008572.

The previous prime is 21008531. The next prime is 21008579. The reversal of 21008573 is 37580012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20403289 + 605284 = 4517^2 + 778^2 .

It is a cyclic number.

It is not a de Polignac number, because 21008573 - 2²² = 16814269 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21008579) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504286 + 10504287.

It is an arithmetic number, because the mean of its divisors is an integer number (10504287).

Almost surely, 2^21008573 is an apocalyptic number.

It is an amenable number.

21008573 is a deficient number, since it is larger than the sum of its proper divisors (1).

21008573 is an equidigital number, since it uses as much as digits as its factorization.

21008573 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 21008573 is about 4583.5109904963. The cubic root of 21008573 is about 275.9299557954.

Adding to 21008573 its reverse (37580012), we get a palindrome (58588585).

The spelling of 21008573 in words is "twenty-one million, eight thousand, five hundred seventy-three".