21663423 has 32 divisors (see below), whose sum is σ = 34372800. Its totient is φ = 13436928.

The previous prime is 21663419. The next prime is 21663427. The reversal of 21663423 is 32436612.

21663423 is a `hidden beast` number, since 2 + 1 + 6 + 634 + 23 = 666.

It is an interprime number because it is at equal distance from previous prime (21663419) and next prime (21663427).

It is not a de Polignac number, because 21663423 - 2² = 21663419 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663427) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 49815 + ... + 50247.

It is an arithmetic number, because the mean of its divisors is an integer number (1074150).

Almost surely, 2^21663423 is an apocalyptic number.

21663423 is a deficient number, since it is larger than the sum of its proper divisors (12709377).

21663423 is a wasteful number, since it uses less digits than its factorization.

21663423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 568 (or 562 counting only the distinct ones).

The product of its digits is 5184, while the sum is 27.

The square root of 21663423 is about 4654.3982425229. The cubic root of 21663423 is about 278.7676409703.

The spelling of 21663423 in words is "twenty-one million, six hundred sixty-three thousand, four hundred twenty-three".