997871909 has 4 divisors (see below), whose sum is σ = 1001581740. Its totient is φ = 994162080.

The previous prime is 997871881. The next prime is 997871911. The reversal of 997871909 is 909178799.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 91259809 + 906612100 = 9553^2 + 30110^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-997871909 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (997871929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1854512 + ... + 1855049.

It is an arithmetic number, because the mean of its divisors is an integer number (250395435).

Almost surely, 2^997871909 is an apocalyptic number.

It is an amenable number.

997871909 is a deficient number, since it is larger than the sum of its proper divisors (3709831).

997871909 is a wasteful number, since it uses less digits than its factorization.

997871909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3709830.

The product of its (nonzero) digits is 2571912, while the sum is 59.

The square root of 997871909 is about 31589.1106079294. The cubic root of 997871909 is about 999.2901325408.

The spelling of 997871909 in words is "nine hundred ninety-seven million, eight hundred seventy-one thousand, nine hundred nine".