21840365 has 8 divisors (see below), whose sum is σ = 26354328. Its totient is φ = 17375040.

The previous prime is 21840361. The next prime is 21840389. The reversal of 21840365 is 56304812.

It can be written as a sum of positive squares in 4 ways, for example, as 40804 + 21799561 = 202^2 + 4669^2 .

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

It is not a de Polignac number, because 21840365 - 2² = 21840361 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 (21840361) 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, 11162 + ... + 12971.

It is an arithmetic number, because the mean of its divisors is an integer number (3294291).

Almost surely, 2^21840365 is an apocalyptic number.

It is an amenable number.

21840365 is a deficient number, since it is larger than the sum of its proper divisors (4513963).

21840365 is a wasteful number, since it uses less digits than its factorization.

21840365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24319.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21840365 is about 4673.3676294510. The cubic root of 21840365 is about 279.5245545358.

The spelling of 21840365 in words is "twenty-one million, eight hundred forty thousand, three hundred sixty-five".