21408973 has 2 divisors, whose sum is σ = 21408974. Its totient is φ = 21408972.

The previous prime is 21408971. The next prime is 21408983. The reversal of 21408973 is 37980412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14455204 + 6953769 = 3802^2 + 2637^2 .

It is a cyclic number.

It is not a de Polignac number, because 21408973 - 2¹ = 21408971 is a prime.

Together with 21408971, it forms a pair of twin primes.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21408971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704486 + 10704487.

It is an arithmetic number, because the mean of its divisors is an integer number (10704487).

Almost surely, 2^21408973 is an apocalyptic number.

It is an amenable number.

21408973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21408973 is an equidigital number, since it uses as much as digits as its factorization.

21408973 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21408973 is about 4626.9831423942. The cubic root of 21408973 is about 277.6719082002.

The spelling of 21408973 in words is "twenty-one million, four hundred eight thousand, nine hundred seventy-three".