721513251 has 20 divisors (see below), whose sum is σ = 1112588224. Its totient is φ = 465490800.

The previous prime is 721513229. The next prime is 721513259. The reversal of 721513251 is 152315127.

It is not a de Polignac number, because 721513251 - 2⁶ = 721513187 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721513259) 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 19 ways as a sum of consecutive naturals, for example, 141160 + ... + 146181.

Almost surely, 2^721513251 is an apocalyptic number.

721513251 is a deficient number, since it is larger than the sum of its proper divisors (391074973).

721513251 is a wasteful number, since it uses less digits than its factorization.

721513251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287384 (or 287375 counting only the distinct ones).

The product of its digits is 2100, while the sum is 27.

The square root of 721513251 is about 26860.9986969956. The cubic root of 721513251 is about 896.9084256802.

Adding to 721513251 its reverse (152315127), we get a palindrome (873828378).

The spelling of 721513251 in words is "seven hundred twenty-one million, five hundred thirteen thousand, two hundred fifty-one".