155221724721 has 32 divisors (see below), whose sum is σ = 249161011200. Its totient is φ = 83967770880.

The previous prime is 155221724701. The next prime is 155221724771. The reversal of 155221724721 is 127427122551.

155221724721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 155221724721 - 2⁹ = 155221724209 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 155221724721.

It is not an unprimeable number, because it can be changed into a prime (155221724701) 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 31 ways as a sum of consecutive naturals, for example, 400120 + ... + 685958.

It is an arithmetic number, because the mean of its divisors is an integer number (7786281600).

Almost surely, 2^155221724721 is an apocalyptic number.

It is an amenable number.

155221724721 is a deficient number, since it is larger than the sum of its proper divisors (93939286479).

155221724721 is a wasteful number, since it uses less digits than its factorization.

155221724721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287229.

The product of its digits is 78400, while the sum is 39.

The spelling of 155221724721 in words is "one hundred fifty-five billion, two hundred twenty-one million, seven hundred twenty-four thousand, seven hundred twenty-one".