251231009 has 2 divisors, whose sum is σ = 251231010. Its totient is φ = 251231008.

The previous prime is 251230997. The next prime is 251231041. The reversal of 251231009 is 900132152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 203689984 + 47541025 = 14272^2 + 6895^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-251231009 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is equal to p_13743014 and since 251231009 and 13743014 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (251231609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125615504 + 125615505.

It is an arithmetic number, because the mean of its divisors is an integer number (125615505).

Almost surely, 2^251231009 is an apocalyptic number.

It is an amenable number.

251231009 is a deficient number, since it is larger than the sum of its proper divisors (1).

251231009 is an equidigital number, since it uses as much as digits as its factorization.

251231009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 251231009 is about 15850.2684204401. The cubic root of 251231009 is about 630.9928152199.

The spelling of 251231009 in words is "two hundred fifty-one million, two hundred thirty-one thousand, nine".