249721 has 2 divisors, whose sum is σ = 249722. Its totient is φ = 249720.

The previous prime is 249703. The next prime is 249727. The reversal of 249721 is 127942.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 230400 + 19321 = 480^2 + 139^2 .

It is a cyclic number.

It is not a de Polignac number, because 249721 - 2⁷ = 249593 is a prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (249727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 124860 + 124861.

It is an arithmetic number, because the mean of its divisors is an integer number (124861).

2²⁴⁹⁷²¹ is an apocalyptic number.

It is an amenable number.

249721 is a deficient number, since it is larger than the sum of its proper divisors (1).

249721 is an equidigital number, since it uses as much as digits as its factorization.

249721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1008, while the sum is 25.

The square root of 249721 is about 499.7209221155. The cubic root of 249721 is about 62.9726092402.

The spelling of 249721 in words is "two hundred forty-nine thousand, seven hundred twenty-one".