21161609 has 16 divisors (see below), whose sum is σ = 24938496. Its totient is φ = 17581200.

The previous prime is 21161603. The next prime is 21161627. The reversal of 21161609 is 90616112.

It is not a de Polignac number, because 21161609 - 2¹⁶ = 21096073 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21161603) 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 15 ways as a sum of consecutive naturals, for example, 42854 + ... + 43344.

It is an arithmetic number, because the mean of its divisors is an integer number (1558656).

Almost surely, 2^21161609 is an apocalyptic number.

It is an amenable number.

21161609 is a deficient number, since it is larger than the sum of its proper divisors (3776887).

21161609 is a wasteful number, since it uses less digits than its factorization.

21161609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 676.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21161609 is about 4600.1748879798. The cubic root of 21161609 is about 276.5983352482.

It can be divided in two parts, 2 and 1161609, that added together give a palindrome (1161611).

The spelling of 21161609 in words is "twenty-one million, one hundred sixty-one thousand, six hundred nine".