21834821 has 2 divisors, whose sum is σ = 21834822. Its totient is φ = 21834820.

The previous prime is 21834803. The next prime is 21834823. The reversal of 21834821 is 12843812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21808900 + 25921 = 4670^2 + 161^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21834821 is a prime.

It is a Sophie Germain prime.

Together with 21834823, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21834823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10917410 + 10917411.

It is an arithmetic number, because the mean of its divisors is an integer number (10917411).

Almost surely, 2^21834821 is an apocalyptic number.

It is an amenable number.

21834821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21834821 is an equidigital number, since it uses as much as digits as its factorization.

21834821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3072, while the sum is 29.

The square root of 21834821 is about 4672.7744435185. The cubic root of 21834821 is about 279.5009008519.

The spelling of 21834821 in words is "twenty-one million, eight hundred thirty-four thousand, eight hundred twenty-one".