21008857487 has 4 divisors (see below), whose sum is σ = 21009182376. Its totient is φ = 21008532600.

The previous prime is 21008857477. The next prime is 21008857577. The reversal of 21008857487 is 78475880012.

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 21008857487 - 2⁸ = 21008857231 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 (21008857417) 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, 28793 + ... + 206994.

It is an arithmetic number, because the mean of its divisors is an integer number (5252295594).

Almost surely, 2^21008857487 is an apocalyptic number.

21008857487 is a deficient number, since it is larger than the sum of its proper divisors (324889).

21008857487 is an equidigital number, since it uses as much as digits as its factorization.

21008857487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 324888.

The product of its (nonzero) digits is 1003520, while the sum is 50.

The spelling of 21008857487 in words is "twenty-one billion, eight million, eight hundred fifty-seven thousand, four hundred eighty-seven".