21285509671 has 4 divisors (see below), whose sum is σ = 21286374912. Its totient is φ = 21284644432.

The previous prime is 21285509653. The next prime is 21285509701. The reversal of 21285509671 is 17690558212.

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

It is a cyclic number.

It is not a de Polignac number, because 21285509671 - 2⁹ = 21285509159 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21285507671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 394606 + ... + 445291.

It is an arithmetic number, because the mean of its divisors is an integer number (5321593728).

Almost surely, 2^21285509671 is an apocalyptic number.

21285509671 is a deficient number, since it is larger than the sum of its proper divisors (865241).

21285509671 is an equidigital number, since it uses as much as digits as its factorization.

21285509671 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 865240.

The product of its (nonzero) digits is 302400, while the sum is 46.

The spelling of 21285509671 in words is "twenty-one billion, two hundred eighty-five million, five hundred nine thousand, six hundred seventy-one".