21163621 has 2 divisors, whose sum is σ = 21163622. Its totient is φ = 21163620.

The previous prime is 21163603. The next prime is 21163627. The reversal of 21163621 is 12636112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18062500 + 3101121 = 4250^2 + 1761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21163621 - 2¹⁵ = 21130853 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21163592 and 21163601.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21163627) by changing a digit.

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 as a sum of consecutive naturals, namely, 10581810 + 10581811.

It is an arithmetic number, because the mean of its divisors is an integer number (10581811).

Almost surely, 2^21163621 is an apocalyptic number.

It is an amenable number.

21163621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21163621 is an equidigital number, since it uses as much as digits as its factorization.

21163621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432, while the sum is 22.

The square root of 21163621 is about 4600.3935701198. The cubic root of 21163621 is about 276.6071010941.

Adding to 21163621 its reverse (12636112), we get a palindrome (33799733).

The spelling of 21163621 in words is "twenty-one million, one hundred sixty-three thousand, six hundred twenty-one".