21004609 has 2 divisors, whose sum is σ = 21004610. Its totient is φ = 21004608.

The previous prime is 21004603. The next prime is 21004619. The reversal of 21004609 is 90640012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20930625 + 73984 = 4575^2 + 272^2 .

It is a cyclic number.

It is not a de Polignac number, because 21004609 - 2³ = 21004601 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21004609.

It is not a weakly prime, because it can be changed into another prime (21004601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502304 + 10502305.

It is an arithmetic number, because the mean of its divisors is an integer number (10502305).

Almost surely, 2^21004609 is an apocalyptic number.

It is an amenable number.

21004609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004609 is an equidigital number, since it uses as much as digits as its factorization.

21004609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21004609 is about 4583.0785504942. The cubic root of 21004609 is about 275.9126001006.

The spelling of 21004609 in words is "twenty-one million, four thousand, six hundred nine".