20665188637 has 4 divisors (see below), whose sum is σ = 20666046940. Its totient is φ = 20664330336.

The previous prime is 20665188611. The next prime is 20665188689. The reversal of 20665188637 is 73688156602.

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 19262386521 + 1402802116 = 138789^2 + 37454^2 .

It is a cyclic number.

It is not a de Polignac number, because 20665188637 - 2²³ = 20656800029 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 (20665188437) 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, 391962 + ... + 441547.

It is an arithmetic number, because the mean of its divisors is an integer number (5166511735).

Almost surely, 2^20665188637 is an apocalyptic number.

It is an amenable number.

20665188637 is a deficient number, since it is larger than the sum of its proper divisors (858303).

20665188637 is an equidigital number, since it uses as much as digits as its factorization.

20665188637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 858302.

The product of its (nonzero) digits is 2903040, while the sum is 52.

The spelling of 20665188637 in words is "twenty billion, six hundred sixty-five million, one hundred eighty-eight thousand, six hundred thirty-seven".