21366973 has 2 divisors, whose sum is σ = 21366974. Its totient is φ = 21366972.

The previous prime is 21366971. The next prime is 21367009. The reversal of 21366973 is 37966312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17749369 + 3617604 = 4213^2 + 1902^2 .

It is a cyclic number.

It is not a de Polignac number, because 21366973 - 2¹ = 21366971 is a prime.

Together with 21366971, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21366971) 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, 10683486 + 10683487.

It is an arithmetic number, because the mean of its divisors is an integer number (10683487).

Almost surely, 2^21366973 is an apocalyptic number.

It is an amenable number.

21366973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21366973 is an equidigital number, since it uses as much as digits as its factorization.

21366973 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 40824, while the sum is 37.

The square root of 21366973 is about 4622.4423198132. The cubic root of 21366973 is about 277.4902109471.

The spelling of 21366973 in words is "twenty-one million, three hundred sixty-six thousand, nine hundred seventy-three".