55111721 has 12 divisors (see below), whose sum is σ = 65070288. Its totient is φ = 46530792.

The previous prime is 55111717. The next prime is 55111733. The reversal of 55111721 is 12711155.

It is not a de Polignac number, because 55111721 - 2² = 55111717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (55111711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5111 + ... + 11676.

It is an arithmetic number, because the mean of its divisors is an integer number (5422524).

Almost surely, 2^55111721 is an apocalyptic number.

It is an amenable number.

55111721 is a deficient number, since it is larger than the sum of its proper divisors (9958567).

55111721 is a wasteful number, since it uses less digits than its factorization.

55111721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16868 (or 16861 counting only the distinct ones).

The product of its digits is 350, while the sum is 23.

The square root of 55111721 is about 7423.7268942223. The cubic root of 55111721 is about 380.5525686811.

Adding to 55111721 its reverse (12711155), we get a palindrome (67822876).

The spelling of 55111721 in words is "fifty-five million, one hundred eleven thousand, seven hundred twenty-one".