721145251 has 4 divisors (see below), whose sum is σ = 729833832. Its totient is φ = 712456672.

The previous prime is 721145231. The next prime is 721145261. The reversal of 721145251 is 152541127.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721145251 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721145221) 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 3 ways as a sum of consecutive naturals, for example, 4344166 + ... + 4344331.

It is an arithmetic number, because the mean of its divisors is an integer number (182458458).

Almost surely, 2^721145251 is an apocalyptic number.

721145251 is a deficient number, since it is larger than the sum of its proper divisors (8688581).

721145251 is an equidigital number, since it uses as much as digits as its factorization.

721145251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8688580.

The product of its digits is 2800, while the sum is 28.

The square root of 721145251 is about 26854.1477429465. The cubic root of 721145251 is about 896.7559136134.

Adding to 721145251 its reverse (152541127), we get a palindrome (873686378).

The spelling of 721145251 in words is "seven hundred twenty-one million, one hundred forty-five thousand, two hundred fifty-one".