998172509 has 2 divisors, whose sum is σ = 998172510. Its totient is φ = 998172508.

The previous prime is 998172491. The next prime is 998172517. The reversal of 998172509 is 905271899.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 818532100 + 179640409 = 28610^2 + 13403^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-998172509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (998172529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499086254 + 499086255.

It is an arithmetic number, because the mean of its divisors is an integer number (499086255).

Almost surely, 2^998172509 is an apocalyptic number.

It is an amenable number.

998172509 is a deficient number, since it is larger than the sum of its proper divisors (1).

998172509 is an equidigital number, since it uses as much as digits as its factorization.

998172509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 408240, while the sum is 50.

The square root of 998172509 is about 31593.8682183743. The cubic root of 998172509 is about 999.3904648758.

The spelling of 998172509 in words is "nine hundred ninety-eight million, one hundred seventy-two thousand, five hundred nine".