249189657721 has 3 divisors (see below), whose sum is σ = 249190156911. Its totient is φ = 249189158532.

The previous prime is 249189657709. The next prime is 249189657727. The reversal of 249189657721 is 127756981942.

The square root of 249189657721 is 499189.

It is a perfect power (a square), and thus also a powerful number.

249189657721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 105715369321 + 143474288400 = 325139^2 + 378780^2 .

It is not a de Polignac number, because 249189657721 - 2⁷ = 249189657593 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 249189657721.

It is not an unprimeable number, because it can be changed into a prime (249189657727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 249595 + ... + 748783.

It is an arithmetic number, because the mean of its divisors is an integer number (83063385637).

Almost surely, 2^249189657721 is an apocalyptic number.

249189657721 is the 499189-th square number.

249189657721 is the 249595-th centered octagonal number.

It is an amenable number.

249189657721 is a deficient number, since it is larger than the sum of its proper divisors (499190).

249189657721 is an frugal number, since it uses more digits than its factorization.

249189657721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 998378 (or 499189 counting only the distinct ones).

The product of its digits is 15240960, while the sum is 61.

The spelling of 249189657721 in words is "two hundred forty-nine billion, one hundred eighty-nine million, six hundred fifty-seven thousand, seven hundred twenty-one".