21684373 has 4 divisors (see below), whose sum is σ = 22432140. Its totient is φ = 20936608.

The previous prime is 21684371. The next prime is 21684409. The reversal of 21684373 is 37348612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13972644 + 7711729 = 3738^2 + 2777^2 .

It is not a de Polignac number, because 21684373 - 2¹ = 21684371 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21684371) 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 in 3 ways as a sum of consecutive naturals, for example, 373840 + ... + 373897.

It is an arithmetic number, because the mean of its divisors is an integer number (5608035).

Almost surely, 2^21684373 is an apocalyptic number.

It is an amenable number.

21684373 is a deficient number, since it is larger than the sum of its proper divisors (747767).

21684373 is an equidigital number, since it uses as much as digits as its factorization.

21684373 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 747766.

The product of its digits is 24192, while the sum is 34.

The square root of 21684373 is about 4656.6482581359. The cubic root of 21684373 is about 278.8574744263.

The spelling of 21684373 in words is "twenty-one million, six hundred eighty-four thousand, three hundred seventy-three".