21309630 has 16 divisors (see below), whose sum is σ = 51143184. Its totient is φ = 5682560.

The previous prime is 21309623. The next prime is 21309643. The reversal of 21309630 is 3690312.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21309630.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 355131 + ... + 355190.

It is an arithmetic number, because the mean of its divisors is an integer number (3196449).

Almost surely, 2^21309630 is an apocalyptic number.

21309630 is an abundant number, since it is smaller than the sum of its proper divisors (29833554).

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

21309630 is a wasteful number, since it uses less digits than its factorization.

21309630 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 710331.

The product of its (nonzero) digits is 972, while the sum is 24.

The square root of 21309630 is about 4616.2354792623. The cubic root of 21309630 is about 277.2417530896.

Adding to 21309630 its reverse (3690312), we get a palindrome (24999942).

The spelling of 21309630 in words is "twenty-one million, three hundred nine thousand, six hundred thirty".