20791776721 has 2 divisors, whose sum is σ = 20791776722. Its totient is φ = 20791776720.

The previous prime is 20791776701. The next prime is 20791776757. The reversal of 20791776721 is 12767719702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19948455121 + 843321600 = 141239^2 + 29040^2 .

It is a cyclic number.

It is not a de Polignac number, because 20791776721 - 2¹⁵ = 20791743953 is a prime.

It is not a weakly prime, because it can be changed into another prime (20791776701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10395888360 + 10395888361.

It is an arithmetic number, because the mean of its divisors is an integer number (10395888361).

Almost surely, 2^20791776721 is an apocalyptic number.

It is an amenable number.

20791776721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20791776721 is an equidigital number, since it uses as much as digits as its factorization.

20791776721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 518616, while the sum is 49.

The spelling of 20791776721 in words is "twenty billion, seven hundred ninety-one million, seven hundred seventy-six thousand, seven hundred twenty-one".