21680471 has 4 divisors (see below), whose sum is σ = 22184712. Its totient is φ = 21176232.

The previous prime is 21680459. The next prime is 21680473. The reversal of 21680471 is 17408612.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21680471 is a prime.

It is a super-3 number, since 3×21680471³ (a number of 23 digits) contains 333 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 (21680473) 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 3 ways as a sum of consecutive naturals, for example, 252056 + ... + 252141.

It is an arithmetic number, because the mean of its divisors is an integer number (5546178).

Almost surely, 2^21680471 is an apocalyptic number.

21680471 is a deficient number, since it is larger than the sum of its proper divisors (504241).

21680471 is an equidigital number, since it uses as much as digits as its factorization.

21680471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 504240.

The product of its (nonzero) digits is 2688, while the sum is 29.

The square root of 21680471 is about 4656.2292684102. The cubic root of 21680471 is about 278.8407470633.

The spelling of 21680471 in words is "twenty-one million, six hundred eighty thousand, four hundred seventy-one".