21840473 has 4 divisors (see below), whose sum is σ = 21849828. Its totient is φ = 21831120.

The previous prime is 21840457. The next prime is 21840479. The reversal of 21840473 is 37404812.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 21187609 + 652864 = 4603^2 + 808^2 .

It is a cyclic number.

It is not a de Polignac number, because 21840473 - 2⁴ = 21840457 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21840479) 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, 2063 + ... + 6923.

It is an arithmetic number, because the mean of its divisors is an integer number (5462457).

Almost surely, 2^21840473 is an apocalyptic number.

It is an amenable number.

21840473 is a deficient number, since it is larger than the sum of its proper divisors (9355).

21840473 is an equidigital number, since it uses as much as digits as its factorization.

21840473 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9354.

The product of its (nonzero) digits is 5376, while the sum is 29.

The square root of 21840473 is about 4673.3791842734. The cubic root of 21840473 is about 279.5250152821.

The spelling of 21840473 in words is "twenty-one million, eight hundred forty thousand, four hundred seventy-three".