21786369 has 16 divisors (see below), whose sum is σ = 33358080. Its totient is φ = 12508560.

The previous prime is 21786361. The next prime is 21786389. The reversal of 21786369 is 96368712.

It is a happy number.

It is not a de Polignac number, because 21786369 - 2³ = 21786361 is a prime.

It is a super-2 number, since 2×21786369² = 949291748408322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21786369.

It is not an unprimeable number, because it can be changed into a prime (21786361) 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, 16747 + ... + 18000.

It is an arithmetic number, because the mean of its divisors is an integer number (2084880).

Almost surely, 2^21786369 is an apocalyptic number.

It is an amenable number.

21786369 is a deficient number, since it is larger than the sum of its proper divisors (11571711).

21786369 is a wasteful number, since it uses less digits than its factorization.

21786369 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34780.

The product of its digits is 108864, while the sum is 42.

The square root of 21786369 is about 4667.5870639978. The cubic root of 21786369 is about 279.2940079724.

It can be divided in two parts, 21786 and 369, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 21786369 in words is "twenty-one million, seven hundred eighty-six thousand, three hundred sixty-nine".