21685469 has 4 divisors (see below), whose sum is σ = 23353596. Its totient is φ = 20017344.

The previous prime is 21685457. The next prime is 21685483. The reversal of 21685469 is 96458612.

It is a happy number.

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 7344100 + 14341369 = 2710^2 + 3787^2 .

It is a cyclic number.

It is not a de Polignac number, because 21685469 - 2¹⁶ = 21619933 is a prime.

It is a super-2 number, since 2×21685469² = 940519131499922, 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 (21685409) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 834044 + ... + 834069.

It is an arithmetic number, because the mean of its divisors is an integer number (5838399).

Almost surely, 2^21685469 is an apocalyptic number.

It is an amenable number.

21685469 is a deficient number, since it is larger than the sum of its proper divisors (1668127).

21685469 is a wasteful number, since it uses less digits than its factorization.

21685469 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1668126.

The product of its digits is 103680, while the sum is 41.

The square root of 21685469 is about 4656.7659378586. The cubic root of 21685469 is about 278.8621724738.

The spelling of 21685469 in words is "twenty-one million, six hundred eighty-five thousand, four hundred sixty-nine".