56181721 has 8 divisors (see below), whose sum is σ = 57074024. Its totient is φ = 55296000.

The previous prime is 56181707. The next prime is 56181731. The reversal of 56181721 is 12718165.

It can be written as a sum of positive squares in 4 ways, for example, as 3459600 + 52722121 = 1860^2 + 7261^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 5-Lehmer number, since φ(56181721) divides (56181721-1)⁵.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-56181721 is a prime.

It is not an unprimeable number, because it can be changed into a prime (56181701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17221 + ... + 20221.

It is an arithmetic number, because the mean of its divisors is an integer number (7134253).

Almost surely, 2^56181721 is an apocalyptic number.

It is an amenable number.

56181721 is a deficient number, since it is larger than the sum of its proper divisors (892303).

56181721 is a wasteful number, since it uses less digits than its factorization.

56181721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3291.

The product of its digits is 3360, while the sum is 31.

The square root of 56181721 is about 7495.4466844879. The cubic root of 56181721 is about 382.9996227843. Note that the first 3 decimals are identical.

Adding to 56181721 its reverse (12718165), we get a palindrome (68899886).

The spelling of 56181721 in words is "fifty-six million, one hundred eighty-one thousand, seven hundred twenty-one".