20840656657 has 16 divisors (see below), whose sum is σ = 22299840000. Its totient is φ = 19433473920.

The previous prime is 20840656621. The next prime is 20840656687. The reversal of 20840656657 is 75665604802.

It is a happy number.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20840656657 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20840656657.

It is not an unprimeable number, because it can be changed into a prime (20840656687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 425373 + ... + 471829.

It is an arithmetic number, because the mean of its divisors is an integer number (1393740000).

Almost surely, 2^20840656657 is an apocalyptic number.

It is an amenable number.

20840656657 is a deficient number, since it is larger than the sum of its proper divisors (1459183343).

20840656657 is a wasteful number, since it uses less digits than its factorization.

20840656657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47016.

The product of its (nonzero) digits is 2419200, while the sum is 49.

The spelling of 20840656657 in words is "twenty billion, eight hundred forty million, six hundred fifty-six thousand, six hundred fifty-seven".