21630223 has 2 divisors, whose sum is σ = 21630224. Its totient is φ = 21630222.

The previous prime is 21630211. The next prime is 21630229. The reversal of 21630223 is 32203612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21630223 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21630223.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21630229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10815111 + 10815112.

It is an arithmetic number, because the mean of its divisors is an integer number (10815112).

Almost surely, 2^21630223 is an apocalyptic number.

21630223 is a deficient number, since it is larger than the sum of its proper divisors (1).

21630223 is an equidigital number, since it uses as much as digits as its factorization.

21630223 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 19.

The square root of 21630223 is about 4650.8303559687. The cubic root of 21630223 is about 278.6251609072.

Adding to 21630223 its reverse (32203612), we get a palindrome (53833835).

The spelling of 21630223 in words is "twenty-one million, six hundred thirty thousand, two hundred twenty-three".