21840393 has 16 divisors (see below), whose sum is σ = 31898880. Its totient is φ = 13230336.

The previous prime is 21840391. The next prime is 21840407. The reversal of 21840393 is 39304812.

It is not a de Polignac number, because 21840393 - 2¹ = 21840391 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21840393.

It is not an unprimeable number, because it can be changed into a prime (21840391) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5905 + ... + 8862.

It is an arithmetic number, because the mean of its divisors is an integer number (1993680).

Almost surely, 2^21840393 is an apocalyptic number.

It is an amenable number.

21840393 is a deficient number, since it is larger than the sum of its proper divisors (10058487).

21840393 is a wasteful number, since it uses less digits than its factorization.

21840393 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14816.

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 21840393 is about 4673.3706251484. The cubic root of 21840393 is about 279.5246739887.

The spelling of 21840393 in words is "twenty-one million, eight hundred forty thousand, three hundred ninety-three".