251491 has 2 divisors, whose sum is σ = 251492.
Its totient is φ = 251490.
The previous prime is 251483. The next prime is 251501. The reversal of 251491 is 194152.
It is a weak prime.
It is a cyclic number.
It is not a de Polignac number, because 251491 - 23 = 251483 is a prime.
It is not a weakly prime, because it can be changed into another prime (251431) 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, 125745 + 125746.
It is an arithmetic number, because the mean of its divisors is an integer number (125746).
2251491 is an apocalyptic number.
251491 is a deficient number, since it is larger than the sum of its proper divisors (1).
251491 is an equidigital number, since it uses as much as digits as its factorization.
251491 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 360, while the sum is 22.
The square root of 251491 is about 501.4887835236.
The cubic root of 251491 is about 63.1210404993.
The spelling of 251491 in words is "two hundred fifty-one thousand, four hundred ninety-one".