21686469 has 24 divisors (see below), whose sum is σ = 33893568. Its totient is φ = 12297600.

The previous prime is 21686449. The next prime is 21686471. The reversal of 21686469 is 96468612.

It is not a de Polignac number, because 21686469 - 2¹³ = 21678277 is a prime.

It is a super-2 number, since 2×21686469² = 940605875375922, 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 21686469.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21686419) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21709 + ... + 22685.

It is an arithmetic number, because the mean of its divisors is an integer number (1412232).

Almost surely, 2^21686469 is an apocalyptic number.

It is an amenable number.

21686469 is a deficient number, since it is larger than the sum of its proper divisors (12207099).

21686469 is a wasteful number, since it uses less digits than its factorization.

21686469 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1145 (or 1138 counting only the distinct ones).

The product of its digits is 124416, while the sum is 42.

The square root of 21686469 is about 4656.8733072739. The cubic root of 21686469 is about 278.8664588754.

It can be divided in two parts, 21686 and 469, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 21686469 in words is "twenty-one million, six hundred eighty-six thousand, four hundred sixty-nine".