21630013 has 2 divisors, whose sum is σ = 21630014. Its totient is φ = 21630012.

The previous prime is 21629977. The next prime is 21630019. The reversal of 21630013 is 31003612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12131289 + 9498724 = 3483^2 + 3082^2 .

It is a cyclic number.

It is not a de Polignac number, because 21630013 - 2⁹ = 21629501 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21630019) 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, 10815006 + 10815007.

It is an arithmetic number, because the mean of its divisors is an integer number (10815007).

Almost surely, 2^21630013 is an apocalyptic number.

It is an amenable number.

21630013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21630013 is an equidigital number, since it uses as much as digits as its factorization.

21630013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108, while the sum is 16.

The square root of 21630013 is about 4650.8077793003. The cubic root of 21630013 is about 278.6242592140.

Adding to 21630013 its reverse (31003612), we get a palindrome (52633625).

It can be divided in two parts, 2163001 and 3, that multiplied together give a triangular number (6489003 = T₃₆₀₂).

The spelling of 21630013 in words is "twenty-one million, six hundred thirty thousand, thirteen".