171899750921 has 2 divisors, whose sum is σ = 171899750922. Its totient is φ = 171899750920.

The previous prime is 171899750863. The next prime is 171899750927. The reversal of 171899750921 is 129057998171.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 161170934521 + 10728816400 = 401461^2 + 103580^2 .

It is a cyclic number.

It is not a de Polignac number, because 171899750921 - 2³⁰ = 170826009097 is a prime.

It is not a weakly prime, because it can be changed into another prime (171899750927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 85949875460 + 85949875461.

It is an arithmetic number, because the mean of its divisors is an integer number (85949875461).

Almost surely, 2^171899750921 is an apocalyptic number.

It is an amenable number.

171899750921 is a deficient number, since it is larger than the sum of its proper divisors (1).

171899750921 is an equidigital number, since it uses as much as digits as its factorization.

171899750921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2857680, while the sum is 59.

The spelling of 171899750921 in words is "one hundred seventy-one billion, eight hundred ninety-nine million, seven hundred fifty thousand, nine hundred twenty-one".