20004000661 has 4 divisors (see below), whose sum is σ = 20051516524. Its totient is φ = 19956484800.

The previous prime is 20004000659. The next prime is 20004000671. The reversal of 20004000661 is 16600040002.

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 7497828100 + 12506172561 = 86590^2 + 111831^2 .

It is a cyclic number.

It is not a de Polignac number, because 20004000661 - 2¹ = 20004000659 is a prime.

It is the 141436-th Hogben number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20004000671) by changing a digit.

It is a nontrivial repunit in base 141435.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23757300 + ... + 23758141.

It is an arithmetic number, because the mean of its divisors is an integer number (5012879131).

Almost surely, 2^20004000661 is an apocalyptic number.

It is an amenable number.

20004000661 is a deficient number, since it is larger than the sum of its proper divisors (47515863).

20004000661 is an equidigital number, since it uses as much as digits as its factorization.

20004000661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47515862.

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 20004000661 its reverse (16600040002), we get a palindrome (36604040663).

The spelling of 20004000661 in words is "twenty billion, four million, six hundred sixty-one", and thus it is an aban number.