21636487 has 2 divisors, whose sum is σ = 21636488. Its totient is φ = 21636486.

The previous prime is 21636473. The next prime is 21636493. The reversal of 21636487 is 78463612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21636487 - 2¹¹ = 21634439 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21636187) 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, 10818243 + 10818244.

It is an arithmetic number, because the mean of its divisors is an integer number (10818244).

Almost surely, 2^21636487 is an apocalyptic number.

21636487 is a deficient number, since it is larger than the sum of its proper divisors (1).

21636487 is an equidigital number, since it uses as much as digits as its factorization.

21636487 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 37.

The square root of 21636487 is about 4651.5037353527. The cubic root of 21636487 is about 278.6520544434.

The spelling of 21636487 in words is "twenty-one million, six hundred thirty-six thousand, four hundred eighty-seven".