21639833 has 2 divisors, whose sum is σ = 21639834. Its totient is φ = 21639832.

The previous prime is 21639823. The next prime is 21639869. The reversal of 21639833 is 33893612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20403289 + 1236544 = 4517^2 + 1112^2 .

It is a cyclic number.

It is not a de Polignac number, because 21639833 - 2⁶ = 21639769 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21639793 and 21639802.

It is not a weakly prime, because it can be changed into another prime (21639823) 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, 10819916 + 10819917.

It is an arithmetic number, because the mean of its divisors is an integer number (10819917).

Almost surely, 2^21639833 is an apocalyptic number.

It is an amenable number.

21639833 is a deficient number, since it is larger than the sum of its proper divisors (1).

21639833 is an equidigital number, since it uses as much as digits as its factorization.

21639833 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 35.

The square root of 21639833 is about 4651.8633900836. The cubic root of 21639833 is about 278.6664178613. Note that the first 3 decimals are identical.

The spelling of 21639833 in words is "twenty-one million, six hundred thirty-nine thousand, eight hundred thirty-three".