217155919981 has 96 divisors (see below), whose sum is σ = 303838359552. Its totient is φ = 152494151040.

The previous prime is 217155919979. The next prime is 217155920027. The reversal of 217155919981 is 189919551712.

It is not a de Polignac number, because 217155919981 - 2¹ = 217155919979 is a prime.

It is a super-2 number, since 2×217155919981² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217155919381) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 239421730 + ... + 239422636.

It is an arithmetic number, because the mean of its divisors is an integer number (3164982912).

Almost surely, 2^217155919981 is an apocalyptic number.

It is an amenable number.

217155919981 is a deficient number, since it is larger than the sum of its proper divisors (86682439571).

217155919981 is a wasteful number, since it uses less digits than its factorization.

217155919981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1719 (or 1712 counting only the distinct ones).

The product of its digits is 2041200, while the sum is 58.

The spelling of 217155919981 in words is "two hundred seventeen billion, one hundred fifty-five million, nine hundred nineteen thousand, nine hundred eighty-one".