21440663 has 4 divisors (see below), whose sum is σ = 21963648. Its totient is φ = 20917680.

The previous prime is 21440647. The next prime is 21440677. The reversal of 21440663 is 36604412.

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 21440663 - 2⁴ = 21440647 is a prime.

It is a Duffinian number.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21440693) 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, 261431 + ... + 261512.

It is an arithmetic number, because the mean of its divisors is an integer number (5490912).

Almost surely, 2^21440663 is an apocalyptic number.

21440663 is a deficient number, since it is larger than the sum of its proper divisors (522985).

21440663 is an equidigital number, since it uses as much as digits as its factorization.

21440663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 522984.

The product of its (nonzero) digits is 3456, while the sum is 26.

The square root of 21440663 is about 4630.4063536584. The cubic root of 21440663 is about 277.8088458702.

The spelling of 21440663 in words is "twenty-one million, four hundred forty thousand, six hundred sixty-three".