721523261 has 2 divisors, whose sum is σ = 721523262. Its totient is φ = 721523260.

The previous prime is 721523239. The next prime is 721523263. The reversal of 721523261 is 162325127.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 495952900 + 225570361 = 22270^2 + 15019^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721523261 is a prime.

Together with 721523263, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721523263) 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, 360761630 + 360761631.

It is an arithmetic number, because the mean of its divisors is an integer number (360761631).

Almost surely, 2^721523261 is an apocalyptic number.

It is an amenable number.

721523261 is a deficient number, since it is larger than the sum of its proper divisors (1).

721523261 is an equidigital number, since it uses as much as digits as its factorization.

721523261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5040, while the sum is 29.

The square root of 721523261 is about 26861.1850259813. The cubic root of 721523261 is about 896.9125734497.

Adding to 721523261 its reverse (162325127), we get a palindrome (883848388).

The spelling of 721523261 in words is "seven hundred twenty-one million, five hundred twenty-three thousand, two hundred sixty-one".