20356720997 has 2 divisors, whose sum is σ = 20356720998. Its totient is φ = 20356720996.

The previous prime is 20356720987. The next prime is 20356720999. The reversal of 20356720997 is 79902765302.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20009234116 + 347486881 = 141454^2 + 18641^2 .

It is a cyclic number.

It is not a de Polignac number, because 20356720997 - 2¹² = 20356716901 is a prime.

Together with 20356720999, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20356720999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10178360498 + 10178360499.

It is an arithmetic number, because the mean of its divisors is an integer number (10178360499).

Almost surely, 2^20356720997 is an apocalyptic number.

It is an amenable number.

20356720997 is a deficient number, since it is larger than the sum of its proper divisors (1).

20356720997 is an equidigital number, since it uses as much as digits as its factorization.

20356720997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1428840, while the sum is 50.

The spelling of 20356720997 in words is "twenty billion, three hundred fifty-six million, seven hundred twenty thousand, nine hundred ninety-seven".