20356771997 has 2 divisors, whose sum is σ = 20356771998. Its totient is φ = 20356771996.

The previous prime is 20356771987. The next prime is 20356772027. The reversal of 20356771997 is 79917765302.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17061323161 + 3295448836 = 130619^2 + 57406^2 .

It is a cyclic number.

It is not a de Polignac number, because 20356771997 - 2⁶ = 20356771933 is a prime.

It is a super-3 number, since 3×20356771997³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20356771987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10178385998 + 10178385999.

It is an arithmetic number, because the mean of its divisors is an integer number (10178385999).

Almost surely, 2^20356771997 is an apocalyptic number.

It is an amenable number.

20356771997 is a deficient number, since it is larger than the sum of its proper divisors (1).

20356771997 is an equidigital number, since it uses as much as digits as its factorization.

20356771997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5000940, while the sum is 56.

The spelling of 20356771997 in words is "twenty billion, three hundred fifty-six million, seven hundred seventy-one thousand, nine hundred ninety-seven".