21802005 has 12 divisors (see below), whose sum is σ = 37790220. Its totient is φ = 11627712.

The previous prime is 21801943. The next prime is 21802009. The reversal of 21802005 is 50020812.

It can be written as a sum of positive squares in 2 ways, for example, as 15421329 + 6380676 = 3927^2 + 2526^2 .

It is not a de Polignac number, because 21802005 - 2⁷ = 21801877 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21802009) by changing a digit.

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, 242200 + ... + 242289.

It is an arithmetic number, because the mean of its divisors is an integer number (3149185).

Almost surely, 2^21802005 is an apocalyptic number.

It is an amenable number.

21802005 is a deficient number, since it is larger than the sum of its proper divisors (15988215).

21802005 is a wasteful number, since it uses less digits than its factorization.

21802005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 484500 (or 484497 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 21802005 is about 4669.2617189444. The cubic root of 21802005 is about 279.3608081015.

Adding to 21802005 its reverse (50020812), we get a palindrome (71822817).

The spelling of 21802005 in words is "twenty-one million, eight hundred two thousand, five".