21686571 has 12 divisors (see below), whose sum is σ = 31856760. Its totient is φ = 14212320.

The previous prime is 21686563. The next prime is 21686579. The reversal of 21686571 is 17568612.

21686571 is a `hidden beast` number, since 2 + 1 + 6 + 86 + 571 = 666.

It is an interprime number because it is at equal distance from previous prime (21686563) and next prime (21686579).

It is not a de Polignac number, because 21686571 - 2³ = 21686563 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21686579) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19890 + ... + 20951.

It is an arithmetic number, because the mean of its divisors is an integer number (2654730).

Almost surely, 2^21686571 is an apocalyptic number.

21686571 is a deficient number, since it is larger than the sum of its proper divisors (10170189).

21686571 is a wasteful number, since it uses less digits than its factorization.

21686571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40906 (or 40903 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21686571 is about 4656.8842588151. The cubic root of 21686571 is about 278.8668960810.

The spelling of 21686571 in words is "twenty-one million, six hundred eighty-six thousand, five hundred seventy-one".