21030756 has 12 divisors (see below), whose sum is σ = 49071792. Its totient is φ = 7010248.

The previous prime is 21030721. The next prime is 21030767. The reversal of 21030756 is 65703012.

It is a tau number, because it is divible by the number of its divisors (12).

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 3 ways as a sum of consecutive naturals, for example, 876270 + ... + 876293.

It is an arithmetic number, because the mean of its divisors is an integer number (4089316).

Almost surely, 2^21030756 is an apocalyptic number.

It is an amenable number.

21030756 is an abundant number, since it is smaller than the sum of its proper divisors (28041036).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21030756 is a wasteful number, since it uses less digits than its factorization.

21030756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1752570 (or 1752568 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 24.

The square root of 21030756 is about 4585.9302218852. The cubic root of 21030756 is about 276.0270399889.

Adding to 21030756 its reverse (65703012), we get a palindrome (86733768).

The spelling of 21030756 in words is "twenty-one million, thirty thousand, seven hundred fifty-six".