21604621 has 2 divisors, whose sum is σ = 21604622. Its totient is φ = 21604620.

The previous prime is 21604601. The next prime is 21604643. The reversal of 21604621 is 12640612.

It is an a-pointer prime, because the next prime (21604643) can be obtained adding 21604621 to its sum of digits (22).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18404100 + 3200521 = 4290^2 + 1789^2 .

It is a cyclic number.

It is not a de Polignac number, because 21604621 - 2⁹ = 21604109 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21604592 and 21604601.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21604601) 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, 10802310 + 10802311.

It is an arithmetic number, because the mean of its divisors is an integer number (10802311).

Almost surely, 2^21604621 is an apocalyptic number.

It is an amenable number.

21604621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21604621 is an equidigital number, since it uses as much as digits as its factorization.

21604621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21604621 is about 4648.0771293084. The cubic root of 21604621 is about 278.5151885840.

The spelling of 21604621 in words is "twenty-one million, six hundred four thousand, six hundred twenty-one".