56721818 has 16 divisors (see below), whose sum is σ = 89069760. Its totient is φ = 27039936.

The previous prime is 56721811. The next prime is 56721827. The reversal of 56721818 is 81812765.

It is an alternating number because its digits alternate between odd and even.

It is not an unprimeable number, because it can be changed into a prime (56721811) 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 7 ways as a sum of consecutive naturals, for example, 13673 + ... + 17331.

It is an arithmetic number, because the mean of its divisors is an integer number (5566860).

Almost surely, 2^56721818 is an apocalyptic number.

56721818 is a deficient number, since it is larger than the sum of its proper divisors (32347942).

56721818 is a wasteful number, since it uses less digits than its factorization.

56721818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4021.

The product of its digits is 26880, while the sum is 38.

The square root of 56721818 is about 7531.3888493425. The cubic root of 56721818 is about 384.2230195020.

The spelling of 56721818 in words is "fifty-six million, seven hundred twenty-one thousand, eight hundred eighteen".