251856949 has 2 divisors, whose sum is σ = 251856950. Its totient is φ = 251856948.

The previous prime is 251856947. The next prime is 251856959. The reversal of 251856949 is 949658152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 251856900 + 49 = 15870^2 + 7^2 .

It is a cyclic number.

It is not a de Polignac number, because 251856949 - 2¹ = 251856947 is a prime.

Together with 251856947, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251856947) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125928474 + 125928475.

It is an arithmetic number, because the mean of its divisors is an integer number (125928475).

Almost surely, 2^251856949 is an apocalyptic number.

It is an amenable number.

251856949 is a deficient number, since it is larger than the sum of its proper divisors (1).

251856949 is an equidigital number, since it uses as much as digits as its factorization.

251856949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 777600, while the sum is 49.

The square root of 251856949 is about 15870.0015437932. The cubic root of 251856949 is about 631.5164184186.

Subtracting from 251856949 its sum of digits (49), we obtain a square (251856900 = 15870²).

It can be divided in two parts, 2518569 and 49, that multiplied together give a square (123409881 = 11109²).

The spelling of 251856949 in words is "two hundred fifty-one million, eight hundred fifty-six thousand, nine hundred forty-nine".