55721257 has 4 divisors (see below), whose sum is σ = 58998996. Its totient is φ = 52443520.

The previous prime is 55721231. The next prime is 55721261. The reversal of 55721257 is 75212755.

55721257 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 75212755 = 5 ⋅15042551.

It can be written as a sum of positive squares in 2 ways, for example, as 48219136 + 7502121 = 6944^2 + 2739^2 .

It is a cyclic number.

It is not a de Polignac number, because 55721257 - 2¹⁹ = 55196969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (55721207) 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 3 ways as a sum of consecutive naturals, for example, 1638844 + ... + 1638877.

It is an arithmetic number, because the mean of its divisors is an integer number (14749749).

Almost surely, 2^55721257 is an apocalyptic number.

It is an amenable number.

55721257 is a deficient number, since it is larger than the sum of its proper divisors (3277739).

55721257 is a wasteful number, since it uses less digits than its factorization.

55721257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3277738.

The product of its digits is 24500, while the sum is 34.

The square root of 55721257 is about 7464.6672397368. The cubic root of 55721257 is about 381.9503992505.

The spelling of 55721257 in words is "fifty-five million, seven hundred twenty-one thousand, two hundred fifty-seven".