21663647 has 2 divisors, whose sum is σ = 21663648. Its totient is φ = 21663646.

The previous prime is 21663623. The next prime is 21663659. The reversal of 21663647 is 74636612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21663647 - 2⁸ = 21663391 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21663247) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10831823 + 10831824.

It is an arithmetic number, because the mean of its divisors is an integer number (10831824).

Almost surely, 2^21663647 is an apocalyptic number.

21663647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21663647 is an equidigital number, since it uses as much as digits as its factorization.

21663647 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 35.

The square root of 21663647 is about 4654.4223057217. The cubic root of 21663647 is about 278.7686017870.

The spelling of 21663647 in words is "twenty-one million, six hundred sixty-three thousand, six hundred forty-seven".