249987721 has 9 divisors (see below), whose sum is σ = 254150631. Its totient is φ = 245892672.

The previous prime is 249987677. The next prime is 249987733. The reversal of 249987721 is 127789942.

The square root of 249987721 is 15811.

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

It can be written as a sum of positive squares in only one way, i.e., 112254025 + 137733696 = 10595^2 + 11736^2 .

It is not a de Polignac number, because 249987721 - 2¹³ = 249979529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (249987781) 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 in 8 ways as a sum of consecutive naturals, for example, 1533586 + ... + 1533748.

It is an arithmetic number, because the mean of its divisors is an integer number (28238959).

Almost surely, 2^249987721 is an apocalyptic number.

249987721 is the 15811-st square number.

249987721 is the 7906-th centered octagonal number.

It is an amenable number.

249987721 is a deficient number, since it is larger than the sum of its proper divisors (4162910).

249987721 is an frugal number, since it uses more digits than its factorization.

249987721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 520 (or 260 counting only the distinct ones).

The product of its digits is 508032, while the sum is 49.

The cubic root of 249987721 is about 629.9502110649.

Multiplying 249987721 by its sum of digits (49), we get a square (12249398329 = 110677²).

The spelling of 249987721 in words is "two hundred forty-nine million, nine hundred eighty-seven thousand, seven hundred twenty-one".