21660851 has 2 divisors, whose sum is σ = 21660852. Its totient is φ = 21660850.

The previous prime is 21660827. The next prime is 21660853. The reversal of 21660851 is 15806612.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21660851 is a prime.

Together with 21660853, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21660853) 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, 10830425 + 10830426.

It is an arithmetic number, because the mean of its divisors is an integer number (10830426).

Almost surely, 2^21660851 is an apocalyptic number.

21660851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660851 is an equidigital number, since it uses as much as digits as its factorization.

21660851 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 21660851 is about 4654.1219365204. The cubic root of 21660851 is about 278.7566082610.

The spelling of 21660851 in words is "twenty-one million, six hundred sixty thousand, eight hundred fifty-one".