721316551 has 4 divisors (see below), whose sum is σ = 759280600. Its totient is φ = 683352504.

The previous prime is 721316537. The next prime is 721316597. The reversal of 721316551 is 155613127.

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 721316551 - 2¹⁹ = 720792263 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721316251) 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, 18981996 + ... + 18982033.

It is an arithmetic number, because the mean of its divisors is an integer number (189820150).

Almost surely, 2^721316551 is an apocalyptic number.

721316551 is a deficient number, since it is larger than the sum of its proper divisors (37964049).

721316551 is a wasteful number, since it uses less digits than its factorization.

721316551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37964048.

The product of its digits is 6300, while the sum is 31.

The square root of 721316551 is about 26857.3370049973. The cubic root of 721316551 is about 896.8269127759.

Adding to 721316551 its reverse (155613127), we get a palindrome (876929678).

The spelling of 721316551 in words is "seven hundred twenty-one million, three hundred sixteen thousand, five hundred fifty-one".