20405559687 has 4 divisors (see below), whose sum is σ = 27207412920. Its totient is φ = 13603706456.

The previous prime is 20405559677. The next prime is 20405559689. The reversal of 20405559687 is 78695550402.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20405559687 is a prime.

It is a super-2 number, since 2×20405559687² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20405559689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3400926612 + ... + 3400926617.

It is an arithmetic number, because the mean of its divisors is an integer number (6801853230).

Almost surely, 2^20405559687 is an apocalyptic number.

20405559687 is a deficient number, since it is larger than the sum of its proper divisors (6801853233).

20405559687 is an equidigital number, since it uses as much as digits as its factorization.

20405559687 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6801853232.

The product of its (nonzero) digits is 3024000, while the sum is 51.

The spelling of 20405559687 in words is "twenty billion, four hundred five million, five hundred fifty-nine thousand, six hundred eighty-seven".