721728226 has 4 divisors (see below), whose sum is σ = 1082592342. Its totient is φ = 360864112.

The previous prime is 721728223. The next prime is 721728257. The reversal of 721728226 is 622827127.

It is a Cunningham number, because it is equal to 26865²+1.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 721728225 + 1 = 26865^2 + 1^2 .

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 as a sum of consecutive naturals, namely, 180432055 + ... + 180432058.

Almost surely, 2^721728226 is an apocalyptic number.

721728226 is a deficient number, since it is larger than the sum of its proper divisors (360864116).

721728226 is a wasteful number, since it uses less digits than its factorization.

721728226 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360864115.

The product of its digits is 37632, while the sum is 37.

The square root of 721728226 is about 26865.0000186116. Note that the first 4 decimals coincide. The cubic root of 721728226 is about 896.9974948425.

The spelling of 721728226 in words is "seven hundred twenty-one million, seven hundred twenty-eight thousand, two hundred twenty-six".