21738663 has 6 divisors (see below), whose sum is σ = 31400304. Its totient is φ = 14492436.

The previous prime is 21738659. The next prime is 21738671. The reversal of 21738663 is 36683712.

It is a happy number.

21738663 is a `hidden beast` number, since 217 + 386 + 63 = 666.

It is not a de Polignac number, because 21738663 - 2² = 21738659 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21738623) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1207695 + ... + 1207712.

It is an arithmetic number, because the mean of its divisors is an integer number (5233384).

Almost surely, 2^21738663 is an apocalyptic number.

21738663 is a deficient number, since it is larger than the sum of its proper divisors (9661641).

21738663 is a wasteful number, since it uses less digits than its factorization.

21738663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2415413 (or 2415410 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 21738663 is about 4662.4739141361. The cubic root of 21738663 is about 279.0900006401.

The spelling of 21738663 in words is "twenty-one million, seven hundred thirty-eight thousand, six hundred sixty-three".