20985821857 has 16 divisors (see below), whose sum is σ = 28176769152. Its totient is φ = 15094696320.

The previous prime is 20985821821. The next prime is 20985821869. The reversal of 20985821857 is 75812858902.

It is not a de Polignac number, because 20985821857 - 2⁷ = 20985821729 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20985821798 and 20985821807.

It is not an unprimeable number, because it can be changed into a prime (20985822857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10481428 + ... + 10483429.

It is an arithmetic number, because the mean of its divisors is an integer number (1761048072).

Almost surely, 2^20985821857 is an apocalyptic number.

It is an amenable number.

20985821857 is a deficient number, since it is larger than the sum of its proper divisors (7190947295).

20985821857 is a wasteful number, since it uses less digits than its factorization.

20985821857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20964888.

The product of its (nonzero) digits is 3225600, while the sum is 55.

The spelling of 20985821857 in words is "twenty billion, nine hundred eighty-five million, eight hundred twenty-one thousand, eight hundred fifty-seven".