21805070 has 32 divisors (see below), whose sum is σ = 45130176. Its totient is φ = 7430400.

The previous prime is 21805037. The next prime is 21805073. The reversal of 21805070 is 7050812.

It is a super-2 number, since 2×21805070² = 950922155409800, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21805073) 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 15 ways as a sum of consecutive naturals, for example, 11810 + ... + 13530.

It is an arithmetic number, because the mean of its divisors is an integer number (1410318).

Almost surely, 2^21805070 is an apocalyptic number.

21805070 is an abundant number, since it is smaller than the sum of its proper divisors (23325106).

21805070 is a wasteful number, since it uses less digits than its factorization.

21805070 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1916.

The product of its (nonzero) digits is 560, while the sum is 23.

The square root of 21805070 is about 4669.5899177551. The cubic root of 21805070 is about 279.3738986522.

Adding to 21805070 its reverse (7050812), we get a palindrome (28855882).

The spelling of 21805070 in words is "twenty-one million, eight hundred five thousand, seventy".