21215630 has 16 divisors (see below), whose sum is σ = 38649744.
Its totient is φ = 8383680.
The previous prime is 21215627. The next prime is 21215657. The reversal of 21215630 is 3651212.
It is a Curzon number.
It is a congruent number.
It is an unprimeable number.
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, 11951 + ... + 13610.
It is an arithmetic number, because the mean of its divisors is an integer number (2415609).
Almost surely, 221215630 is an apocalyptic number.
21215630 is a deficient number, since it is larger than the sum of its proper divisors (17434114).
21215630 is a wasteful number, since it uses less digits than its factorization.
21215630 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 25651.
The product of its (nonzero) digits is 360, while the sum is 20.
The square root of 21215630 is about 4606.0427701010.
The cubic root of 21215630 is about 276.8335004477.
Adding to 21215630 its reverse (3651212), we get a palindrome (24866842).
The spelling of 21215630 in words is "twenty-one million, two hundred fifteen thousand, six hundred thirty".