20565169681 has 4 divisors (see below), whose sum is σ = 23503051072. Its totient is φ = 17627288292.

The previous prime is 20565169673. The next prime is 20565169693. The reversal of 20565169681 is 18696156502.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18696156502 = 2 ⋅9348078251.

It is a cyclic number.

It is not a de Polignac number, because 20565169681 - 2³ = 20565169673 is a prime.

It is a super-2 number, since 2×20565169681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20565169621) 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, 1468940685 + ... + 1468940698.

It is an arithmetic number, because the mean of its divisors is an integer number (5875762768).

Almost surely, 2^20565169681 is an apocalyptic number.

It is an amenable number.

20565169681 is a deficient number, since it is larger than the sum of its proper divisors (2937881391).

20565169681 is an equidigital number, since it uses as much as digits as its factorization.

20565169681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2937881390.

The product of its (nonzero) digits is 777600, while the sum is 49.

The spelling of 20565169681 in words is "twenty billion, five hundred sixty-five million, one hundred sixty-nine thousand, six hundred eighty-one".