20781732397 has 2 divisors, whose sum is σ = 20781732398.
Its totient is φ = 20781732396.
The previous prime is 20781732371. The next prime is 20781732403. The reversal of 20781732397 is 79323718702.
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., 17942334601 + 2839397796 = 133949^2 + 53286^2
It is a cyclic number.
It is not a de Polignac number, because 20781732397 - 27 = 20781732269 is a prime.
It is a self number, because there is not a number n which added to its sum of digits gives 20781732397.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (20781732347) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10390866198 + 10390866199.
It is an arithmetic number, because the mean of its divisors is an integer number (10390866199).
Almost surely, 220781732397 is an apocalyptic number.
It is an amenable number.
20781732397 is a deficient number, since it is larger than the sum of its proper divisors (1).
20781732397 is an equidigital number, since it uses as much as digits as its factorization.
20781732397 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 889056, while the sum is 49.
The spelling of 20781732397 in words is "twenty billion, seven hundred eighty-one million, seven hundred thirty-two thousand, three hundred ninety-seven".