21211643 has 2 divisors, whose sum is σ = 21211644. Its totient is φ = 21211642.

The previous prime is 21211613. The next prime is 21211709. The reversal of 21211643 is 34611212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21211643 - 2⁸ = 21211387 is a prime.

It is not a weakly prime, because it can be changed into another prime (21211613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605821 + 10605822.

It is an arithmetic number, because the mean of its divisors is an integer number (10605822).

Almost surely, 2^21211643 is an apocalyptic number.

21211643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211643 is an equidigital number, since it uses as much as digits as its factorization.

21211643 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 288, while the sum is 20.

The square root of 21211643 is about 4605.6099487473. The cubic root of 21211643 is about 276.8161578200.

Adding to 21211643 its reverse (34611212), we get a palindrome (55822855).

The spelling of 21211643 in words is "twenty-one million, two hundred eleven thousand, six hundred forty-three".