72121721555 has 16 divisors (see below), whose sum is σ = 93232931904. Its totient is φ = 53242273920.

The previous prime is 72121721543. The next prime is 72121721627. The reversal of 72121721555 is 55512712127.

It is a happy number.

It is not a de Polignac number, because 72121721555 - 2¹⁸ = 72121459411 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33557 + ... + 381273.

It is an arithmetic number, because the mean of its divisors is an integer number (5827058244).

Almost surely, 2^72121721555 is an apocalyptic number.

72121721555 is a deficient number, since it is larger than the sum of its proper divisors (21111210349).

72121721555 is a wasteful number, since it uses less digits than its factorization.

72121721555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350926.

The product of its digits is 49000, while the sum is 38.

The spelling of 72121721555 in words is "seventy-two billion, one hundred twenty-one million, seven hundred twenty-one thousand, five hundred fifty-five".