21105671 has 2 divisors, whose sum is σ = 21105672. Its totient is φ = 21105670.

The previous prime is 21105661. The next prime is 21105677. The reversal of 21105671 is 17650112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21105671 - 2¹⁰ = 21104647 is a prime.

It is a Sophie Germain 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 (21105677) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552835 + 10552836.

It is an arithmetic number, because the mean of its divisors is an integer number (10552836).

Almost surely, 2^21105671 is an apocalyptic number.

21105671 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105671 is an equidigital number, since it uses as much as digits as its factorization.

21105671 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21105671 is about 4594.0908785090. The cubic root of 21105671 is about 276.3544027760.

Adding to 21105671 its reverse (17650112), we get a palindrome (38755783).

The spelling of 21105671 in words is "twenty-one million, one hundred five thousand, six hundred seventy-one".