21105730 has 32 divisors (see below), whose sum is σ = 39656448. Its totient is φ = 8078400.

The previous prime is 21105709. The next prime is 21105739. The reversal of 21105730 is 3750112.

It is a junction number, because it is equal to n+sod(n) for n = 21105698 and 21105707.

It is not an unprimeable number, because it can be changed into a prime (21105739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31600 + ... + 32260.

It is an arithmetic number, because the mean of its divisors is an integer number (1239264).

Almost surely, 2^21105730 is an apocalyptic number.

21105730 is a deficient number, since it is larger than the sum of its proper divisors (18550718).

21105730 is a wasteful number, since it uses less digits than its factorization.

21105730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 802.

The product of its (nonzero) digits is 210, while the sum is 19.

The square root of 21105730 is about 4594.0972997968. The cubic root of 21105730 is about 276.3546602880.

Adding to 21105730 its reverse (3750112), we get a palindrome (24855842).

The spelling of 21105730 in words is "twenty-one million, one hundred five thousand, seven hundred thirty".