38721720217 has 2 divisors, whose sum is σ = 38721720218. Its totient is φ = 38721720216.

The previous prime is 38721720209. The next prime is 38721720221. The reversal of 38721720217 is 71202712783.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21161229961 + 17560490256 = 145469^2 + 132516^2 .

It is a cyclic number.

It is not a de Polignac number, because 38721720217 - 2³ = 38721720209 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 38721720217.

It is not a weakly prime, because it can be changed into another prime (38721720227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19360860108 + 19360860109.

It is an arithmetic number, because the mean of its divisors is an integer number (19360860109).

Almost surely, 2^38721720217 is an apocalyptic number.

It is an amenable number.

38721720217 is a deficient number, since it is larger than the sum of its proper divisors (1).

38721720217 is an equidigital number, since it uses as much as digits as its factorization.

38721720217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 65856, while the sum is 40.

The spelling of 38721720217 in words is "thirty-eight billion, seven hundred twenty-one million, seven hundred twenty thousand, two hundred seventeen".