21109973 has 2 divisors, whose sum is σ = 21109974. Its totient is φ = 21109972.

The previous prime is 21109939. The next prime is 21109987. The reversal of 21109973 is 37990112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20232004 + 877969 = 4498^2 + 937^2 .

It is a cyclic number.

It is not a de Polignac number, because 21109973 - 2²² = 16915669 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21109273) 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, 10554986 + 10554987.

It is an arithmetic number, because the mean of its divisors is an integer number (10554987).

Almost surely, 2^21109973 is an apocalyptic number.

It is an amenable number.

21109973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21109973 is an equidigital number, since it uses as much as digits as its factorization.

21109973 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 21109973 is about 4594.5590648070. The cubic root of 21109973 is about 276.3731780753.

The spelling of 21109973 in words is "twenty-one million, one hundred nine thousand, nine hundred seventy-three".