21003601 has 2 divisors, whose sum is σ = 21003602. Its totient is φ = 21003600.

The previous prime is 21003599. The next prime is 21003637. The reversal of 21003601 is 10630012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19793601 + 1210000 = 4449^2 + 1100^2 .

It is a cyclic number.

It is not a de Polignac number, because 21003601 - 2¹ = 21003599 is a prime.

Together with 21003599, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21003001) 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, 10501800 + 10501801.

It is an arithmetic number, because the mean of its divisors is an integer number (10501801).

Almost surely, 2^21003601 is an apocalyptic number.

It is an amenable number.

21003601 is a deficient number, since it is larger than the sum of its proper divisors (1).

21003601 is an equidigital number, since it uses as much as digits as its factorization.

21003601 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21003601 is about 4582.9685794253. The cubic root of 21003601 is about 275.9081863971.

Adding to 21003601 its reverse (10630012), we get a palindrome (31633613).

The spelling of 21003601 in words is "twenty-one million, three thousand, six hundred one".