21006930 has 64 divisors (see below), whose sum is σ = 58060800. Its totient is φ = 4764864.

The previous prime is 21006907. The next prime is 21006941. The reversal of 21006930 is 3960012.

It is a super-2 number, since 2×21006930² = 882582216049800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

21006930 is a modest number, since divided by 6930 gives 2100 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 21006897 and 21006906.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 34771 + ... + 35369.

It is an arithmetic number, because the mean of its divisors is an integer number (907200).

Almost surely, 2^21006930 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21006930, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29030400).

21006930 is an abundant number, since it is smaller than the sum of its proper divisors (37053870).

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

21006930 is a wasteful number, since it uses less digits than its factorization.

21006930 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 783.

The product of its (nonzero) digits is 324, while the sum is 21.

The square root of 21006930 is about 4583.3317575755. The cubic root of 21006930 is about 275.9227624664.

Adding to 21006930 its reverse (3960012), we get a palindrome (24966942).

The spelling of 21006930 in words is "twenty-one million, six thousand, nine hundred thirty".