20828843561 has 4 divisors (see below), whose sum is σ = 20834418000. Its totient is φ = 20823269124.

The previous prime is 20828843557. The next prime is 20828843591. The reversal of 20828843561 is 16534882802.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16534882802 = 2 ⋅8267441401.

It is a cyclic number.

It is not a de Polignac number, because 20828843561 - 2² = 20828843557 is a prime.

It is a super-2 number, since 2×20828843561² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20828843531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2781611 + ... + 2789088.

It is an arithmetic number, because the mean of its divisors is an integer number (5208604500).

Almost surely, 2^20828843561 is an apocalyptic number.

It is an amenable number.

20828843561 is a deficient number, since it is larger than the sum of its proper divisors (5574439).

20828843561 is an equidigital number, since it uses as much as digits as its factorization.

20828843561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5574438.

The product of its (nonzero) digits is 737280, while the sum is 47.

The spelling of 20828843561 in words is "twenty billion, eight hundred twenty-eight million, eight hundred forty-three thousand, five hundred sixty-one".