21163505 has 12 divisors (see below), whose sum is σ = 27915636. Its totient is φ = 15391200.

The previous prime is 21163481. The next prime is 21163507. The reversal of 21163505 is 50536112.

It can be written as a sum of positive squares in 2 ways, for example, as 9759376 + 11404129 = 3124^2 + 3377^2 .

It is not a de Polignac number, because 21163505 - 2²² = 16969201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21163507) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 16886 + ... + 18095.

It is an arithmetic number, because the mean of its divisors is an integer number (2326303).

Almost surely, 2^21163505 is an apocalyptic number.

It is an amenable number.

21163505 is a deficient number, since it is larger than the sum of its proper divisors (6752131).

21163505 is a wasteful number, since it uses less digits than its factorization.

21163505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35008 (or 34997 counting only the distinct ones).

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 21163505 is about 4600.3809624856. The cubic root of 21163505 is about 276.6065957225.

Adding to 21163505 its reverse (50536112), we get a palindrome (71699617).

The spelling of 21163505 in words is "twenty-one million, one hundred sixty-three thousand, five hundred five".