21804637 has 2 divisors, whose sum is σ = 21804638. Its totient is φ = 21804636.

The previous prime is 21804623. The next prime is 21804641. The reversal of 21804637 is 73640812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21427641 + 376996 = 4629^2 + 614^2 .

It is a cyclic number.

It is not a de Polignac number, because 21804637 - 2¹¹ = 21802589 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21804599 and 21804608.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21804037) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10902318 + 10902319.

It is an arithmetic number, because the mean of its divisors is an integer number (10902319).

Almost surely, 2^21804637 is an apocalyptic number.

It is an amenable number.

21804637 is a deficient number, since it is larger than the sum of its proper divisors (1).

21804637 is an equidigital number, since it uses as much as digits as its factorization.

21804637 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 21804637 is about 4669.5435537106. The cubic root of 21804637 is about 279.3720493927.

The spelling of 21804637 in words is "twenty-one million, eight hundred four thousand, six hundred thirty-seven".