21066641 has 2 divisors, whose sum is σ = 21066642. Its totient is φ = 21066640.

The previous prime is 21066613. The next prime is 21066677. The reversal of 21066641 is 14666012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18190225 + 2876416 = 4265^2 + 1696^2 .

It is a cyclic number.

It is not a de Polignac number, because 21066641 - 2²² = 16872337 is a prime.

It is equal to p_1333943 and since 21066641 and 1333943 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21066641.

It is not a weakly prime, because it can be changed into another prime (21066601) 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, 10533320 + 10533321.

It is an arithmetic number, because the mean of its divisors is an integer number (10533321).

Almost surely, 2^21066641 is an apocalyptic number.

It is an amenable number.

21066641 is a deficient number, since it is larger than the sum of its proper divisors (1).

21066641 is an equidigital number, since it uses as much as digits as its factorization.

21066641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 21066641 is about 4589.8410647864. The cubic root of 21066641 is about 276.1839467253.

The spelling of 21066641 in words is "twenty-one million, sixty-six thousand, six hundred forty-one".