20881920346561 has 4 divisors (see below), whose sum is σ = 20881945127124. Its totient is φ = 20881895566000.

The previous prime is 20881920346519. The next prime is 20881920346579. The reversal of 20881920346561 is 16564302918802.

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 14529201734961 + 6352718611600 = 3811719^2 + 2520460^2 .

It is a cyclic number.

It is not a de Polignac number, because 20881920346561 - 2⁷ = 20881920346433 is a prime.

It is a super-3 number, since 3×20881920346561³ (a number of 41 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20881920346361) 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, 11080090 + ... + 12827011.

It is an arithmetic number, because the mean of its divisors is an integer number (5220486281781).

Almost surely, 2^{20881920346561} is an apocalyptic number.

It is an amenable number.

20881920346561 is a deficient number, since it is larger than the sum of its proper divisors (24780563).

20881920346561 is an equidigital number, since it uses as much as digits as its factorization.

20881920346561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24780562.

The product of its (nonzero) digits is 4976640, while the sum is 55.

The spelling of 20881920346561 in words is "twenty trillion, eight hundred eighty-one billion, nine hundred twenty million, three hundred forty-six thousand, five hundred sixty-one".