211506981517 has 18 divisors (see below), whose sum is σ = 229187216958. Its totient is φ = 194035664448.

The previous prime is 211506981509. The next prime is 211506981523. The reversal of 211506981517 is 715189605112.

It can be written as a sum of positive squares in 9 ways, for example, as 58230033481 + 153276948036 = 241309^2 + 391506^2 .

It is not a de Polignac number, because 211506981517 - 2³ = 211506981509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211506981557) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 379725003 + ... + 379725559.

Almost surely, 2^211506981517 is an apocalyptic number.

It is an amenable number.

211506981517 is a deficient number, since it is larger than the sum of its proper divisors (17680235441).

211506981517 is an frugal number, since it uses more digits than its factorization.

211506981517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1585 (or 799 counting only the distinct ones).

The product of its (nonzero) digits is 151200, while the sum is 46.

The spelling of 211506981517 in words is "two hundred eleven billion, five hundred six million, nine hundred eighty-one thousand, five hundred seventeen".