721504405128 has 64 divisors (see below), whose sum is σ = 1942600766400. Its totient is φ = 221991194880.

The previous prime is 721504405117. The next prime is 721504405129. The reversal of 721504405128 is 821504405127.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is not an unprimeable number, because it can be changed into a prime (721504405129) 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 15 ways as a sum of consecutive naturals, for example, 9581143 + ... + 9656153.

It is an arithmetic number, because the mean of its divisors is an integer number (30353136975).

Almost surely, 2^721504405128 is an apocalyptic number.

721504405128 is a gapful number since it is divisible by the number (78) formed by its first and last digit.

It is an amenable number.

721504405128 is an abundant number, since it is smaller than the sum of its proper divisors (1221096361272).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

721504405128 is a wasteful number, since it uses less digits than its factorization.

721504405128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105862 (or 105858 counting only the distinct ones).

The product of its (nonzero) digits is 89600, while the sum is 39.

Subtracting 721504405128 from its reverse (821504405127), we obtain a palindrome (99999999999).

The spelling of 721504405128 in words is "seven hundred twenty-one billion, five hundred four million, four hundred five thousand, one hundred twenty-eight".