21840073 has 4 divisors (see below), whose sum is σ = 21953428. Its totient is φ = 21726720.

The previous prime is 21840061. The next prime is 21840079. The reversal of 21840073 is 37004812.

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 12616704 + 9223369 = 3552^2 + 3037^2 .

It is a cyclic number.

It is not a de Polignac number, because 21840073 - 2⁹ = 21839561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21840079) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 56388 + ... + 56773.

It is an arithmetic number, because the mean of its divisors is an integer number (5488357).

Almost surely, 2^21840073 is an apocalyptic number.

It is an amenable number.

21840073 is a deficient number, since it is larger than the sum of its proper divisors (113355).

21840073 is a wasteful number, since it uses less digits than its factorization.

21840073 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113354.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21840073 is about 4673.3363884916. The cubic root of 21840073 is about 279.5233088067.

Adding to 21840073 its reverse (37004812), we get a palindrome (58844885).

The spelling of 21840073 in words is "twenty-one million, eight hundred forty thousand, seventy-three".