20851043077 has 4 divisors (see below), whose sum is σ = 20851731180. Its totient is φ = 20850354976.

The previous prime is 20851043053. The next prime is 20851043113. The reversal of 20851043077 is 77034015802.

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 3783972196 + 17067070881 = 61514^2 + 130641^2 .

It is a cyclic number.

It is not a de Polignac number, because 20851043077 - 2³¹ = 18703559429 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20851043377) 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 3 ways as a sum of consecutive naturals, for example, 296398 + ... + 359935.

It is an arithmetic number, because the mean of its divisors is an integer number (5212932795).

Almost surely, 2^20851043077 is an apocalyptic number.

It is an amenable number.

20851043077 is a deficient number, since it is larger than the sum of its proper divisors (688103).

20851043077 is an equidigital number, since it uses as much as digits as its factorization.

20851043077 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 688102.

The product of its (nonzero) digits is 47040, while the sum is 37.

Adding to 20851043077 its reverse (77034015802), we get a palindrome (97885058879).

The spelling of 20851043077 in words is "twenty billion, eight hundred fifty-one million, forty-three thousand, seventy-seven".