20681451649 has 4 divisors (see below), whose sum is σ = 20681851140. Its totient is φ = 20681052160.

The previous prime is 20681451619. The next prime is 20681451671. The reversal of 20681451649 is 94615418602.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8453515249 + 12227936400 = 91943^2 + 110580^2 .

It is a cyclic number.

It is not a de Polignac number, because 20681451649 - 2⁵ = 20681451617 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20681451599 and 20681451608.

It is not an unprimeable number, because it can be changed into a prime (20681451619) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 108064 + ... + 230305.

It is an arithmetic number, because the mean of its divisors is an integer number (5170462785).

Almost surely, 2^20681451649 is an apocalyptic number.

It is an amenable number.

20681451649 is a deficient number, since it is larger than the sum of its proper divisors (399491).

20681451649 is an equidigital number, since it uses as much as digits as its factorization.

20681451649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 399490.

The product of its (nonzero) digits is 414720, while the sum is 46.

The spelling of 20681451649 in words is "twenty billion, six hundred eighty-one million, four hundred fifty-one thousand, six hundred forty-nine".