20645959657 has 4 divisors (see below), whose sum is σ = 20646269316. Its totient is φ = 20645650000.

The previous prime is 20645959603. The next prime is 20645959661. The reversal of 20645959657 is 75695954602.

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 12523624281 + 8122335376 = 111909^2 + 90124^2 .

It is a cyclic number.

It is not a de Polignac number, because 20645959657 - 2¹¹ = 20645957609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20645959687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9094 + ... + 203407.

It is an arithmetic number, because the mean of its divisors is an integer number (5161567329).

Almost surely, 2^20645959657 is an apocalyptic number.

It is an amenable number.

20645959657 is a deficient number, since it is larger than the sum of its proper divisors (309659).

20645959657 is an equidigital number, since it uses as much as digits as its factorization.

20645959657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309658.

The product of its (nonzero) digits is 20412000, while the sum is 58.

The spelling of 20645959657 in words is "twenty billion, six hundred forty-five million, nine hundred fifty-nine thousand, six hundred fifty-seven".