20356721321 has 2 divisors, whose sum is σ = 20356721322. Its totient is φ = 20356721320.

The previous prime is 20356721269. The next prime is 20356721327. The reversal of 20356721321 is 12312765302.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15257190400 + 5099530921 = 123520^2 + 71411^2 .

It is a cyclic number.

It is not a de Polignac number, because 20356721321 - 2¹⁰ = 20356720297 is a prime.

It is a super-2 number, since 2×20356721321² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20356721327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10178360660 + 10178360661.

It is an arithmetic number, because the mean of its divisors is an integer number (10178360661).

Almost surely, 2^20356721321 is an apocalyptic number.

It is an amenable number.

20356721321 is a deficient number, since it is larger than the sum of its proper divisors (1).

20356721321 is an equidigital number, since it uses as much as digits as its factorization.

20356721321 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15120, while the sum is 32.

The spelling of 20356721321 in words is "twenty billion, three hundred fifty-six million, seven hundred twenty-one thousand, three hundred twenty-one".