21066623 has 4 divisors (see below), whose sum is σ = 21363408. Its totient is φ = 20769840.

The previous prime is 21066613. The next prime is 21066641. The reversal of 21066623 is 32666012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21066623 - 2⁴ = 21066607 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21066592 and 21066601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21066613) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 148286 + ... + 148427.

It is an arithmetic number, because the mean of its divisors is an integer number (5340852).

Almost surely, 2^21066623 is an apocalyptic number.

21066623 is a deficient number, since it is larger than the sum of its proper divisors (296785).

21066623 is an equidigital number, since it uses as much as digits as its factorization.

21066623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296784.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 21066623 is about 4589.8391039338. The cubic root of 21066623 is about 276.1838680652.

The spelling of 21066623 in words is "twenty-one million, sixty-six thousand, six hundred twenty-three".