20634448661 has 4 divisors (see below), whose sum is σ = 20648382924. Its totient is φ = 20620514400.

The previous prime is 20634448591. The next prime is 20634448673. The reversal of 20634448661 is 16684443602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16684443602 = 2 ⋅8342221801.

It can be written as a sum of positive squares in 2 ways, for example, as 16459350436 + 4175098225 = 128294^2 + 64615^2 .

It is a cyclic number.

It is not a de Polignac number, because 20634448661 - 2²⁶ = 20567339797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20634448361) 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, 6964910 + ... + 6967871.

It is an arithmetic number, because the mean of its divisors is an integer number (5162095731).

Almost surely, 2^20634448661 is an apocalyptic number.

It is an amenable number.

20634448661 is a deficient number, since it is larger than the sum of its proper divisors (13934263).

20634448661 is a wasteful number, since it uses less digits than its factorization.

20634448661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13934262.

The product of its (nonzero) digits is 663552, while the sum is 44.

The spelling of 20634448661 in words is "twenty billion, six hundred thirty-four million, four hundred forty-eight thousand, six hundred sixty-one".