21806369 has 8 divisors (see below), whose sum is σ = 24505152. Its totient is φ = 19253520.

The previous prime is 21806353. The next prime is 21806381. The reversal of 21806369 is 96360812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21806369 - 2⁴ = 21806353 is a prime.

It is a super-2 number, since 2×21806369² = 951035457928322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21806329) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36167 + ... + 36764.

It is an arithmetic number, because the mean of its divisors is an integer number (3063144).

Almost surely, 2^21806369 is an apocalyptic number.

It is an amenable number.

21806369 is a deficient number, since it is larger than the sum of its proper divisors (2698783).

21806369 is a wasteful number, since it uses less digits than its factorization.

21806369 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72967.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 21806369 is about 4669.7290071266. The cubic root of 21806369 is about 279.3794462838.

The spelling of 21806369 in words is "twenty-one million, eight hundred six thousand, three hundred sixty-nine".