21705023 has 8 divisors (see below), whose sum is σ = 22234368. Its totient is φ = 21178584.

The previous prime is 21705007. The next prime is 21705029. The reversal of 21705023 is 32050712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21705023 - 2⁴ = 21705007 is a prime.

It is a super-2 number, since 2×21705023² = 942216046861058, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21704986 and 21705004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21705029) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24140 + ... + 25022.

It is an arithmetic number, because the mean of its divisors is an integer number (2779296).

Almost surely, 2^21705023 is an apocalyptic number.

21705023 is a deficient number, since it is larger than the sum of its proper divisors (529345).

21705023 is an equidigital number, since it uses as much as digits as its factorization.

21705023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1453.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 21705023 is about 4658.8649905315. The cubic root of 21705023 is about 278.9459648784.

Adding to 21705023 its reverse (32050712), we get a palindrome (53755735).

The spelling of 21705023 in words is "twenty-one million, seven hundred five thousand, twenty-three".