21663023 has 4 divisors (see below), whose sum is σ = 21968208. Its totient is φ = 21357840.

The previous prime is 21662989. The next prime is 21663041. The reversal of 21663023 is 32036612.

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 21663023 - 2⁶ = 21662959 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21663023.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 152486 + ... + 152627.

It is an arithmetic number, because the mean of its divisors is an integer number (5492052).

Almost surely, 2^21663023 is an apocalyptic number.

21663023 is a deficient number, since it is larger than the sum of its proper divisors (305185).

21663023 is an equidigital number, since it uses as much as digits as its factorization.

21663023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 305184.

The product of its (nonzero) digits is 1296, while the sum is 23.

The square root of 21663023 is about 4654.3552722155. The cubic root of 21663023 is about 278.7659252097.

Adding to 21663023 its reverse (32036612), we get a palindrome (53699635).

The spelling of 21663023 in words is "twenty-one million, six hundred sixty-three thousand, twenty-three".