21066823 has 2 divisors, whose sum is σ = 21066824. Its totient is φ = 21066822.

The previous prime is 21066821. The next prime is 21066833. The reversal of 21066823 is 32866012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21066823 - 2¹ = 21066821 is a prime.

It is a super-2 number, since 2×21066823² = 887622062626658, which contains 22 as substring.

Together with 21066821, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21066791 and 21066800.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21066821) 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, 10533411 + 10533412.

It is an arithmetic number, because the mean of its divisors is an integer number (10533412).

Almost surely, 2^21066823 is an apocalyptic number.

21066823 is a deficient number, since it is larger than the sum of its proper divisors (1).

21066823 is an equidigital number, since it uses as much as digits as its factorization.

21066823 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 21066823 is about 4589.8608911382. The cubic root of 21066823 is about 276.1847420638.

The spelling of 21066823 in words is "twenty-one million, sixty-six thousand, eight hundred twenty-three".