21011843 has 2 divisors, whose sum is σ = 21011844. Its totient is φ = 21011842.

The previous prime is 21011839. The next prime is 21011869. The reversal of 21011843 is 34811012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21011843 - 2² = 21011839 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21011873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505921 + 10505922.

It is an arithmetic number, because the mean of its divisors is an integer number (10505922).

Almost surely, 2^21011843 is an apocalyptic number.

21011843 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011843 is an equidigital number, since it uses as much as digits as its factorization.

21011843 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21011843 is about 4583.8676900626. The cubic root of 21011843 is about 275.9442712869.

Adding to 21011843 its reverse (34811012), we get a palindrome (55822855).

The spelling of 21011843 in words is "twenty-one million, eleven thousand, eight hundred forty-three".