21408671 has 2 divisors, whose sum is σ = 21408672. Its totient is φ = 21408670.

The previous prime is 21408659. The next prime is 21408679. The reversal of 21408671 is 17680412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21408671 - 2¹⁰ = 21407647 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21408679) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704335 + 10704336.

It is an arithmetic number, because the mean of its divisors is an integer number (10704336).

Almost surely, 2^21408671 is an apocalyptic number.

21408671 is a deficient number, since it is larger than the sum of its proper divisors (1).

21408671 is an equidigital number, since it uses as much as digits as its factorization.

21408671 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2688, while the sum is 29.

The square root of 21408671 is about 4626.9505076238. The cubic root of 21408671 is about 277.6706025590.

The spelling of 21408671 in words is "twenty-one million, four hundred eight thousand, six hundred seventy-one".