21807405 has 12 divisors (see below), whose sum is σ = 37799580. Its totient is φ = 11630592.

The previous prime is 21807377. The next prime is 21807419. The reversal of 21807405 is 50470812.

It can be written as a sum of positive squares in 2 ways, for example, as 6456681 + 15350724 = 2541^2 + 3918^2 .

It is not a de Polignac number, because 21807405 - 2⁶ = 21807341 is a prime.

It is a congruent number.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 242260 + ... + 242349.

It is an arithmetic number, because the mean of its divisors is an integer number (3149965).

Almost surely, 2^21807405 is an apocalyptic number.

It is an amenable number.

21807405 is a deficient number, since it is larger than the sum of its proper divisors (15992175).

21807405 is a wasteful number, since it uses less digits than its factorization.

21807405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 484620 (or 484617 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21807405 is about 4669.8399330170. The cubic root of 21807405 is about 279.3838705650.

The spelling of 21807405 in words is "twenty-one million, eight hundred seven thousand, four hundred five".