20781777413 has 16 divisors (see below), whose sum is σ = 21273859440. Its totient is φ = 20297012736.

The previous prime is 20781777403. The next prime is 20781777437. The reversal of 20781777413 is 31477718702.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 119727364 + 20662050049 = 10942^2 + 143743^2 .

It is a cyclic number.

It is not a de Polignac number, because 20781777413 - 2⁸ = 20781777157 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 (20781777403) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2413031 + ... + 2421627.

It is an arithmetic number, because the mean of its divisors is an integer number (1329616215).

Almost surely, 2^20781777413 is an apocalyptic number.

It is an amenable number.

20781777413 is a deficient number, since it is larger than the sum of its proper divisors (492082027).

20781777413 is a wasteful number, since it uses less digits than its factorization.

20781777413 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9016.

The product of its (nonzero) digits is 460992, while the sum is 47.

The spelling of 20781777413 in words is "twenty billion, seven hundred eighty-one million, seven hundred seventy-seven thousand, four hundred thirteen".