21208871 has 2 divisors, whose sum is σ = 21208872. Its totient is φ = 21208870.

The previous prime is 21208841. The next prime is 21208879. The reversal of 21208871 is 17880212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21208871 - 2¹⁰ = 21207847 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21208879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10604435 + 10604436.

It is an arithmetic number, because the mean of its divisors is an integer number (10604436).

Almost surely, 2^21208871 is an apocalyptic number.

21208871 is a deficient number, since it is larger than the sum of its proper divisors (1).

21208871 is an equidigital number, since it uses as much as digits as its factorization.

21208871 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 21208871 is about 4605.3090015763. The cubic root of 21208871 is about 276.8040989110.

The spelling of 21208871 in words is "twenty-one million, two hundred eight thousand, eight hundred seventy-one".