21385669 has 4 divisors (see below), whose sum is σ = 21403180. Its totient is φ = 21368160.

The previous prime is 21385649. The next prime is 21385681. The reversal of 21385669 is 96658312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15697444 + 5688225 = 3962^2 + 2385^2 .

It is a cyclic number.

It is not a de Polignac number, because 21385669 - 2⁹ = 21385157 is a prime.

It is a super-2 number, since 2×21385669² = 914693677155122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21385649) 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 3 ways as a sum of consecutive naturals, for example, 6774 + ... + 9415.

It is an arithmetic number, because the mean of its divisors is an integer number (5350795).

Almost surely, 2^21385669 is an apocalyptic number.

It is an amenable number.

21385669 is a deficient number, since it is larger than the sum of its proper divisors (17511).

21385669 is a wasteful number, since it uses less digits than its factorization.

21385669 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17510.

The product of its digits is 77760, while the sum is 40.

The square root of 21385669 is about 4624.4641851786. The cubic root of 21385669 is about 277.5711215589.

The spelling of 21385669 in words is "twenty-one million, three hundred eighty-five thousand, six hundred sixty-nine".