20765742781 has 12 divisors (see below), whose sum is σ = 24160278780. Its totient is φ = 17796105600.

The previous prime is 20765742769. The next prime is 20765742883. The reversal of 20765742781 is 18724756702.

It can be written as a sum of positive squares in 2 ways, for example, as 16164833881 + 4600908900 = 127141^2 + 67830^2 .

It is not a de Polignac number, because 20765742781 - 2⁷ = 20765742653 is a prime.

It is a super-2 number, since 2×20765742781² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20765742721) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 273381 + ... + 340981.

It is an arithmetic number, because the mean of its divisors is an integer number (2013356565).

Almost surely, 2^20765742781 is an apocalyptic number.

It is an amenable number.

20765742781 is a deficient number, since it is larger than the sum of its proper divisors (3394535999).

20765742781 is an equidigital number, since it uses as much as digits as its factorization.

20765742781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73884 (or 73877 counting only the distinct ones).

The product of its (nonzero) digits is 1317120, while the sum is 49.

The spelling of 20765742781 in words is "twenty billion, seven hundred sixty-five million, seven hundred forty-two thousand, seven hundred eighty-one".