20845481561 has 4 divisors (see below), whose sum is σ = 21564291300. Its totient is φ = 20126671824.

The previous prime is 20845481551. The next prime is 20845481567. The reversal of 20845481561 is 16518454802.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12846862336 + 7998619225 = 113344^2 + 89435^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20845481561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20845481567) 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, 359404826 + ... + 359404883.

It is an arithmetic number, because the mean of its divisors is an integer number (5391072825).

Almost surely, 2^20845481561 is an apocalyptic number.

It is an amenable number.

20845481561 is a deficient number, since it is larger than the sum of its proper divisors (718809739).

20845481561 is an equidigital number, since it uses as much as digits as its factorization.

20845481561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 718809738.

The product of its (nonzero) digits is 307200, while the sum is 44.

The spelling of 20845481561 in words is "twenty billion, eight hundred forty-five million, four hundred eighty-one thousand, five hundred sixty-one".