20647390865 has 8 divisors (see below), whose sum is σ = 24856030248. Its totient is φ = 16465138560.

The previous prime is 20647390823. The next prime is 20647390873. The reversal of 20647390865 is 56809374602.

It is a happy number.

It is a Cunningham number, because it is equal to 143692²+1.

It can be written as a sum of positive squares in 4 ways, for example, as 131698576 + 20515692289 = 11476^2 + 143233^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-20647390865 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6595046 + ... + 6598175.

It is an arithmetic number, because the mean of its divisors is an integer number (3107003781).

Almost surely, 2^20647390865 is an apocalyptic number.

It is an amenable number.

20647390865 is a deficient number, since it is larger than the sum of its proper divisors (4208639383).

20647390865 is a wasteful number, since it uses less digits than its factorization.

20647390865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13193539.

The product of its (nonzero) digits is 2177280, while the sum is 50.

The spelling of 20647390865 in words is "twenty billion, six hundred forty-seven million, three hundred ninety thousand, eight hundred sixty-five".