20647288515661 has 8 divisors (see below), whose sum is σ = 21497616673848. Its totient is φ = 19813471584000.

The previous prime is 20647288515649. The next prime is 20647288515727. The reversal of 20647288515661 is 16651588274602.

It can be written as a sum of positive squares in 4 ways, for example, as 116874413161 + 20530414102500 = 341869^2 + 4531050^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20647288515661 - 2²⁹ = 20646751644749 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (61).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20647288515661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20647288515761) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4127804080 + ... + 4127809081.

It is an arithmetic number, because the mean of its divisors is an integer number (2687202084231).

Almost surely, 2^{20647288515661} is an apocalyptic number.

It is an amenable number.

20647288515661 is a deficient number, since it is larger than the sum of its proper divisors (850328158187).

20647288515661 is an equidigital number, since it uses as much as digits as its factorization.

20647288515661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8255613263.

The product of its (nonzero) digits is 38707200, while the sum is 61.

The spelling of 20647288515661 in words is "twenty trillion, six hundred forty-seven billion, two hundred eighty-eight million, five hundred fifteen thousand, six hundred sixty-one".