21163509 has 6 divisors (see below), whose sum is σ = 30569526. Its totient is φ = 14109000.

The previous prime is 21163507. The next prime is 21163531. The reversal of 21163509 is 90536112.

21163509 is a `hidden beast` number, since 21 + 1 + 635 + 0 + 9 = 666.

It can be written as a sum of positive squares in only one way, i.e., 18922500 + 2241009 = 4350^2 + 1497^2 .

It is not a de Polignac number, because 21163509 - 2¹ = 21163507 is a prime.

It is a super-2 number, since 2×21163509² = 895788226386162, which contains 22 as substring.

It is a congruent 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 5 ways as a sum of consecutive naturals, for example, 1175742 + ... + 1175759.

It is an arithmetic number, because the mean of its divisors is an integer number (5094921).

Almost surely, 2^21163509 is an apocalyptic number.

It is an amenable number.

21163509 is a deficient number, since it is larger than the sum of its proper divisors (9406017).

21163509 is a wasteful number, since it uses less digits than its factorization.

21163509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2351507 (or 2351504 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 21163509 is about 4600.3813972322. The cubic root of 21163509 is about 276.6066131491.

It can be divided in two parts, 2116 and 3509, that added together give a square (5625 = 75²).

The spelling of 21163509 in words is "twenty-one million, one hundred sixty-three thousand, five hundred nine".