21806169 has 16 divisors (see below), whose sum is σ = 36249600. Its totient is φ = 11327760.

The previous prime is 21806149. The next prime is 21806177. The reversal of 21806169 is 96160812.

It is not a de Polignac number, because 21806169 - 2⁷ = 21806041 is a prime.

It is a super-2 number, since 2×21806169² = 951018012913122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21806149) 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 in 15 ways as a sum of consecutive naturals, for example, 46969 + ... + 47430.

It is an arithmetic number, because the mean of its divisors is an integer number (2265600).

Almost surely, 2^21806169 is an apocalyptic number.

It is an amenable number.

21806169 is a deficient number, since it is larger than the sum of its proper divisors (14443431).

21806169 is a wasteful number, since it uses less digits than its factorization.

21806169 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94420.

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 21806169 is about 4669.7075925587. The cubic root of 21806169 is about 279.3785921594.

It can be divided in two parts, 218061 and 69, that added together give a triangular number (218130 = T₆₆₀).

The spelling of 21806169 in words is "twenty-one million, eight hundred six thousand, one hundred sixty-nine".