21000030 has 16 divisors (see below), whose sum is σ = 50400144. Its totient is φ = 5600000.

The previous prime is 20999999. The next prime is 21000037. The reversal of 21000030 is 3000012.

It is a Harshad number since it is a multiple of its sum of digits (6).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20999982 and 21000018.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000037) 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 7 ways as a sum of consecutive naturals, for example, 349971 + ... + 350030.

It is an arithmetic number, because the mean of its divisors is an integer number (3150009).

Almost surely, 2^21000030 is an apocalyptic number.

21000030 is an abundant number, since it is smaller than the sum of its proper divisors (29400114).

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

21000030 is a wasteful number, since it uses less digits than its factorization.

21000030 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 700011.

The product of its (nonzero) digits is 6, while the sum is 6.

The square root of 21000030 is about 4582.5789682230. The cubic root of 21000030 is about 275.8925490154.

Adding to 21000030 its reverse (3000012), we get a palindrome (24000042).

The spelling of 21000030 in words is "twenty-one million, thirty", and thus it is an aban number and an uban number.