21209973 has 8 divisors (see below), whose sum is σ = 28444128. Its totient is φ = 14057904.

The previous prime is 21209963. The next prime is 21210011. The reversal of 21209973 is 37990212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21209973 - 2⁴ = 21209957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21209963) 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 in 7 ways as a sum of consecutive naturals, for example, 19915 + ... + 20952.

It is an arithmetic number, because the mean of its divisors is an integer number (3555516).

Almost surely, 2^21209973 is an apocalyptic number.

It is an amenable number.

21209973 is a deficient number, since it is larger than the sum of its proper divisors (7234155).

21209973 is a wasteful number, since it uses less digits than its factorization.

21209973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41043.

The product of its (nonzero) digits is 6804, while the sum is 33.

The square root of 21209973 is about 4605.4286445455. The cubic root of 21209973 is about 276.8088930187.

The spelling of 21209973 in words is "twenty-one million, two hundred nine thousand, nine hundred seventy-three".