997172331921 has 6 divisors (see below), whose sum is σ = 1440360035010. Its totient is φ = 664781554608.

The previous prime is 997172331919. The next prime is 997172331937. The reversal of 997172331921 is 129133271799.

997172331921 is a `hidden beast` number, since 99 + 71 + 72 + 331 + 92 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 656279832321 + 340892499600 = 810111^2 + 583860^2 .

It is not a de Polignac number, because 997172331921 - 2¹ = 997172331919 is a prime.

It is not an unprimeable number, because it can be changed into a prime (997172331521) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 55398462876 + ... + 55398462893.

It is an arithmetic number, because the mean of its divisors is an integer number (240060005835).

Almost surely, 2^997172331921 is an apocalyptic number.

It is an amenable number.

997172331921 is a deficient number, since it is larger than the sum of its proper divisors (443187703089).

997172331921 is a wasteful number, since it uses less digits than its factorization.

997172331921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110796925775 (or 110796925772 counting only the distinct ones).

The product of its digits is 1285956, while the sum is 54.

The spelling of 997172331921 in words is "nine hundred ninety-seven billion, one hundred seventy-two million, three hundred thirty-one thousand, nine hundred twenty-one".