217531939657 has 2 divisors, whose sum is σ = 217531939658. Its totient is φ = 217531939656.

The previous prime is 217531939609. The next prime is 217531939663. The reversal of 217531939657 is 756939135712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 111409755961 + 106122183696 = 333781^2 + 325764^2 .

It is a cyclic number.

It is not a de Polignac number, because 217531939657 - 2²⁷ = 217397721929 is a prime.

It is not a weakly prime, because it can be changed into another prime (217531934657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108765969828 + 108765969829.

It is an arithmetic number, because the mean of its divisors is an integer number (108765969829).

Almost surely, 2^217531939657 is an apocalyptic number.

It is an amenable number.

217531939657 is a deficient number, since it is larger than the sum of its proper divisors (1).

217531939657 is an equidigital number, since it uses as much as digits as its factorization.

217531939657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10716300, while the sum is 58.

The spelling of 217531939657 in words is "two hundred seventeen billion, five hundred thirty-one million, nine hundred thirty-nine thousand, six hundred fifty-seven".