1155720721 has 16 divisors (see below), whose sum is σ = 1234986624. Its totient is φ = 1079172864.

The previous prime is 1155720689. The next prime is 1155720737. The reversal of 1155720721 is 1270275511.

It is a cyclic number.

It is not a de Polignac number, because 1155720721 - 2⁵ = 1155720689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1155720521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 170815 + ... + 177451.

It is an arithmetic number, because the mean of its divisors is an integer number (77186664).

Almost surely, 2^1155720721 is an apocalyptic number.

It is an amenable number.

1155720721 is a deficient number, since it is larger than the sum of its proper divisors (79265903).

1155720721 is a wasteful number, since it uses less digits than its factorization.

1155720721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6840.

The product of its (nonzero) digits is 4900, while the sum is 31.

The square root of 1155720721 is about 33995.8927077963. The cubic root of 1155720721 is about 1049.4239382835.

The spelling of 1155720721 in words is "one billion, one hundred fifty-five million, seven hundred twenty thousand, seven hundred twenty-one".