20781568772641 has 4 divisors (see below), whose sum is σ = 20783957742000. Its totient is φ = 20779179803284.

The previous prime is 20781568772639. The next prime is 20781568772669. The reversal of 20781568772641 is 14627786518702.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20781568772641 - 2¹ = 20781568772639 is a prime.

It is a super-2 number, since 2×20781568772641² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20781568776641) 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, 1194471631 + ... + 1194489028.

It is an arithmetic number, because the mean of its divisors is an integer number (5195989435500).

Almost surely, 2^{20781568772641} is an apocalyptic number.

It is an amenable number.

20781568772641 is a deficient number, since it is larger than the sum of its proper divisors (2388969359).

20781568772641 is an equidigital number, since it uses as much as digits as its factorization.

20781568772641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2388969358.

The product of its (nonzero) digits is 63221760, while the sum is 64.

The spelling of 20781568772641 in words is "twenty trillion, seven hundred eighty-one billion, five hundred sixty-eight million, seven hundred seventy-two thousand, six hundred forty-one".