20409278981568 has 56 divisors (see below), whose sum is σ = 54000722031360. Its totient is φ = 6802945416960.

The previous prime is 20409278981561. The next prime is 20409278981579. The reversal of 20409278981568 is 86518987290402.

It is a Cunningham number, because it is equal to 4517663²-1.

It is a Smith number, since the sum of its digits (69) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20409278981561) 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, 7905913 + ... + 10164743.

Almost surely, 2^{20409278981568} is an apocalyptic number.

It is an amenable number.

20409278981568 is an abundant number, since it is smaller than the sum of its proper divisors (33591443049792).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20409278981568 is a wasteful number, since it uses less digits than its factorization.

20409278981568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2305905 (or 2305895 counting only the distinct ones).

The product of its (nonzero) digits is 139345920, while the sum is 69.

The spelling of 20409278981568 in words is "twenty trillion, four hundred nine billion, two hundred seventy-eight million, nine hundred eighty-one thousand, five hundred sixty-eight".