20404258561 has 4 divisors (see below), whose sum is σ = 20404795972. Its totient is φ = 20403721152.

The previous prime is 20404258549. The next prime is 20404258579. The reversal of 20404258561 is 16585240402.

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 17392334400 + 3011924161 = 131880^2 + 54881^2 .

It is a cyclic number.

It is not a de Polignac number, because 20404258561 - 2¹⁷ = 20404127489 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20404258561.

It is not an unprimeable number, because it can be changed into a prime (20404255561) 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, 207036 + ... + 289261.

It is an arithmetic number, because the mean of its divisors is an integer number (5101198993).

Almost surely, 2^20404258561 is an apocalyptic number.

It is an amenable number.

20404258561 is a deficient number, since it is larger than the sum of its proper divisors (537411).

20404258561 is an equidigital number, since it uses as much as digits as its factorization.

20404258561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 537410.

The product of its (nonzero) digits is 76800, while the sum is 37.

Adding to 20404258561 its reverse (16585240402), we get a palindrome (36989498963).

The spelling of 20404258561 in words is "twenty billion, four hundred four million, two hundred fifty-eight thousand, five hundred sixty-one".