20661036781 has 32 divisors (see below), whose sum is σ = 27319965696. Its totient is φ = 15147000000.

The previous prime is 20661036757. The next prime is 20661036793. The reversal of 20661036781 is 18763016602.

It is a happy number.

It is not a de Polignac number, because 20661036781 - 2⁷ = 20661036653 is a prime.

It is a super-2 number, since 2×20661036781² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20661036731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12406 + ... + 203656.

It is an arithmetic number, because the mean of its divisors is an integer number (853748928).

Almost surely, 2^20661036781 is an apocalyptic number.

It is an amenable number.

20661036781 is a deficient number, since it is larger than the sum of its proper divisors (6658928915).

20661036781 is a wasteful number, since it uses less digits than its factorization.

20661036781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191353.

The product of its (nonzero) digits is 72576, while the sum is 40.

The spelling of 20661036781 in words is "twenty billion, six hundred sixty-one million, thirty-six thousand, seven hundred eighty-one".