72555284807721 has 9 divisors (see below), whose sum is σ = 104802114966679. Its totient is φ = 48370172835936.

The previous prime is 72555284807639. The next prime is 72555284807723. The reversal of 72555284807721 is 12770848255527.

It is a happy number.

The square root of 72555284807721 is 8517939.

It is a perfect power (a square), and thus also a powerful number.

72555284807721 is a `hidden beast` number, since 7 + 2 + 5 + 5 + 528 + 4 + 80 + 7 + 7 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 38860324778025 + 33694960029696 = 6233805^2 + 5804736^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 72555284807721 - 2⁴⁵ = 37370912718889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72555284807723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 24134161 + ... + 26973473.

Almost surely, 2^{72555284807721} is an apocalyptic number.

72555284807721 is the 8517939-th square number.

72555284807721 is the 4258970-th centered octagonal number.

It is an amenable number.

72555284807721 is a deficient number, since it is larger than the sum of its proper divisors (32246830158958).

72555284807721 is an frugal number, since it uses more digits than its factorization.

72555284807721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5678632 (or 2839316 counting only the distinct ones).

The product of its (nonzero) digits is 87808000, while the sum is 63.

The spelling of 72555284807721 in words is "seventy-two trillion, five hundred fifty-five billion, two hundred eighty-four million, eight hundred seven thousand, seven hundred twenty-one".