721311551 has 4 divisors (see below), whose sum is σ = 721731912. Its totient is φ = 720891192.

The previous prime is 721311527. The next prime is 721311571. The reversal of 721311551 is 155113127.

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

It is a cyclic number.

It is not a de Polignac number, because 721311551 - 2¹⁴ = 721295167 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 721311551.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721311511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 207596 + ... + 211041.

It is an arithmetic number, because the mean of its divisors is an integer number (180432978).

Almost surely, 2^721311551 is an apocalyptic number.

721311551 is a deficient number, since it is larger than the sum of its proper divisors (420361).

721311551 is a wasteful number, since it uses less digits than its factorization.

721311551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420360.

The product of its digits is 1050, while the sum is 26.

The square root of 721311551 is about 26857.2439204026. The cubic root of 721311551 is about 896.8248405720.

Adding to 721311551 its reverse (155113127), we get a palindrome (876424678).

The spelling of 721311551 in words is "seven hundred twenty-one million, three hundred eleven thousand, five hundred fifty-one".