20851851809 has 8 divisors (see below), whose sum is σ = 20967206400. Its totient is φ = 20736562000.

The previous prime is 20851851767. The next prime is 20851851821. The reversal of 20851851809 is 90815815802.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20851851809 - 2²⁸ = 20583416353 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20851851829) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 721367 + ... + 749715.

It is an arithmetic number, because the mean of its divisors is an integer number (2620900800).

Almost surely, 2^20851851809 is an apocalyptic number.

It is an amenable number.

20851851809 is a deficient number, since it is larger than the sum of its proper divisors (115354591).

20851851809 is a wasteful number, since it uses less digits than its factorization.

20851851809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32391.

The product of its (nonzero) digits is 230400, while the sum is 47.

The spelling of 20851851809 in words is "twenty billion, eight hundred fifty-one million, eight hundred fifty-one thousand, eight hundred nine".