721728225 has 63 divisors (see below), whose sum is σ = 1348577283. Its totient is φ = 382987440.

The previous prime is 721728223. The next prime is 721728257. The reversal of 721728225 is 522827127.

The square root of 721728225 is 26865.

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., 259822161 + 461906064 = 16119^2 + 21492^2 .

It is not a de Polignac number, because 721728225 - 2¹ = 721728223 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 721728225.

It is not an unprimeable number, because it can be changed into a prime (721728223) 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 62 ways as a sum of consecutive naturals, for example, 3626676 + ... + 3626874.

Almost surely, 2^721728225 is an apocalyptic number.

721728225 is a gapful number since it is divisible by the number (75) formed by its first and last digit.

721728225 is the 26865-th square number.

721728225 is the 13433-rd centered octagonal number.

It is an amenable number.

721728225 is a deficient number, since it is larger than the sum of its proper divisors (626849058).

721728225 is an frugal number, since it uses more digits than its factorization.

721728225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 426 (or 207 counting only the distinct ones).

The product of its digits is 31360, while the sum is 36.

The cubic root of 721728225 is about 896.9974944282.

Multiplying 721728225 by its sum of digits (36), we get a square (25982216100 = 161190²).

The spelling of 721728225 in words is "seven hundred twenty-one million, seven hundred twenty-eight thousand, two hundred twenty-five".