21663394 has 8 divisors (see below), whose sum is σ = 32544720. Its totient is φ = 10815156.

The previous prime is 21663391. The next prime is 21663403. The reversal of 21663394 is 49336612.

It is a happy number.

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

It is not an unprimeable number, because it can be changed into a prime (21663391) 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 in 3 ways as a sum of consecutive naturals, for example, 6564 + ... + 9295.

It is an arithmetic number, because the mean of its divisors is an integer number (4068090).

Almost surely, 2^21663394 is an apocalyptic number.

21663394 is a deficient number, since it is larger than the sum of its proper divisors (10881326).

21663394 is a wasteful number, since it uses less digits than its factorization.

21663394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16544.

The product of its digits is 23328, while the sum is 34.

The square root of 21663394 is about 4654.3951271889. The cubic root of 21663394 is about 278.7675165784.

The spelling of 21663394 in words is "twenty-one million, six hundred sixty-three thousand, three hundred ninety-four".