20661416621 has 4 divisors (see below), whose sum is σ = 20662304700. Its totient is φ = 20660528544.

The previous prime is 20661416609. The next prime is 20661416663. The reversal of 20661416621 is 12661416602.

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 6758648521 + 13902768100 = 82211^2 + 117910^2 .

It is a cyclic number.

It is not a de Polignac number, because 20661416621 - 2²⁶ = 20594307757 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 (20661416681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 408176 + ... + 455993.

It is an arithmetic number, because the mean of its divisors is an integer number (5165576175).

Almost surely, 2^20661416621 is an apocalyptic number.

It is an amenable number.

20661416621 is a deficient number, since it is larger than the sum of its proper divisors (888079).

20661416621 is an equidigital number, since it uses as much as digits as its factorization.

20661416621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 888078.

The product of its (nonzero) digits is 20736, while the sum is 35.

The spelling of 20661416621 in words is "twenty billion, six hundred sixty-one million, four hundred sixteen thousand, six hundred twenty-one".