21081673 has 2 divisors, whose sum is σ = 21081674. Its totient is φ = 21081672.

The previous prime is 21081647. The next prime is 21081679. The reversal of 21081673 is 37618012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18731584 + 2350089 = 4328^2 + 1533^2 .

It is a cyclic number.

It is not a de Polignac number, because 21081673 - 2⁹ = 21081161 is a prime.

It is not a weakly prime, because it can be changed into another prime (21081679) 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, 10540836 + 10540837.

It is an arithmetic number, because the mean of its divisors is an integer number (10540837).

Almost surely, 2^21081673 is an apocalyptic number.

It is an amenable number.

21081673 is a deficient number, since it is larger than the sum of its proper divisors (1).

21081673 is an equidigital number, since it uses as much as digits as its factorization.

21081673 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21081673 is about 4591.4783022465. The cubic root of 21081673 is about 276.2496210146.

Adding to 21081673 its reverse (37618012), we get a palindrome (58699685).

The spelling of 21081673 in words is "twenty-one million, eighty-one thousand, six hundred seventy-three".