21630213 has 32 divisors (see below), whose sum is σ = 35512320. Its totient is φ = 12901680.

The previous prime is 21630211. The next prime is 21630223. The reversal of 21630213 is 31203612.

21630213 is a `hidden beast` number, since 21 + 630 + 2 + 13 = 666.

It is not a de Polignac number, because 21630213 - 2¹ = 21630211 is a prime.

It is a super-2 number, since 2×21630213² = 935732228850738, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21630211) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19356 + ... + 20442.

It is an arithmetic number, because the mean of its divisors is an integer number (1109760).

Almost surely, 2^21630213 is an apocalyptic number.

It is an amenable number.

21630213 is a deficient number, since it is larger than the sum of its proper divisors (13882107).

21630213 is a wasteful number, since it uses less digits than its factorization.

21630213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1174 (or 1168 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21630213 is about 4650.8292808917. The cubic root of 21630213 is about 278.6251179696.

Adding to 21630213 its reverse (31203612), we get a palindrome (52833825).

The spelling of 21630213 in words is "twenty-one million, six hundred thirty thousand, two hundred thirteen".