21163145 has 4 divisors (see below), whose sum is σ = 25395780. Its totient is φ = 16930512.

The previous prime is 21163141. The next prime is 21163159. The reversal of 21163145 is 54136112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16096144 + 5067001 = 4012^2 + 2251^2 .

It is a cyclic number.

It is not a de Polignac number, because 21163145 - 2² = 21163141 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21163145.

It is not an unprimeable number, because it can be changed into a prime (21163141) 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 in 3 ways as a sum of consecutive naturals, for example, 2116310 + ... + 2116319.

It is an arithmetic number, because the mean of its divisors is an integer number (6348945).

Almost surely, 2^21163145 is an apocalyptic number.

It is an amenable number.

21163145 is a deficient number, since it is larger than the sum of its proper divisors (4232635).

21163145 is an equidigital number, since it uses as much as digits as its factorization.

21163145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4232634.

The product of its digits is 720, while the sum is 23.

The square root of 21163145 is about 4600.3418351249. The cubic root of 21163145 is about 276.6050273159.

Adding to 21163145 its reverse (54136112), we get a palindrome (75299257).

The spelling of 21163145 in words is "twenty-one million, one hundred sixty-three thousand, one hundred forty-five".