21805707 has 16 divisors (see below), whose sum is σ = 36248832. Its totient is φ = 11327520.

The previous prime is 21805699. The next prime is 21805739. The reversal of 21805707 is 70750812.

It is a happy number.

It is not a de Polignac number, because 21805707 - 2³ = 21805699 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21805507) 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 15 ways as a sum of consecutive naturals, for example, 46968 + ... + 47429.

It is an arithmetic number, because the mean of its divisors is an integer number (2265552).

Almost surely, 2^21805707 is an apocalyptic number.

21805707 is a deficient number, since it is larger than the sum of its proper divisors (14443125).

21805707 is a wasteful number, since it uses less digits than its factorization.

21805707 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94418.

The product of its (nonzero) digits is 3920, while the sum is 30.

The square root of 21805707 is about 4669.6581245312. The cubic root of 21805707 is about 279.3766191119.

It can be divided in two parts, 2180 and 5707, that added together give a palindrome (7887).

The spelling of 21805707 in words is "twenty-one million, eight hundred five thousand, seven hundred seven".