21636533 has 2 divisors, whose sum is σ = 21636534. Its totient is φ = 21636532.

The previous prime is 21636521. The next prime is 21636541. The reversal of 21636533 is 33563612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18601969 + 3034564 = 4313^2 + 1742^2 .

It is a cyclic number.

It is not a de Polignac number, because 21636533 - 2²⁴ = 4859317 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21636496 and 21636505.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21636833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10818266 + 10818267.

It is an arithmetic number, because the mean of its divisors is an integer number (10818267).

Almost surely, 2^21636533 is an apocalyptic number.

It is an amenable number.

21636533 is a deficient number, since it is larger than the sum of its proper divisors (1).

21636533 is an equidigital number, since it uses as much as digits as its factorization.

21636533 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9720, while the sum is 29.

The square root of 21636533 is about 4651.5086799876. The cubic root of 21636533 is about 278.6522519183.

The spelling of 21636533 in words is "twenty-one million, six hundred thirty-six thousand, five hundred thirty-three".