57108721 has 2 divisors, whose sum is σ = 57108722. Its totient is φ = 57108720.

The previous prime is 57108691. The next prime is 57108757. The reversal of 57108721 is 12780175.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 40462321 + 16646400 = 6361^2 + 4080^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-57108721 is a prime.

It is a super-2 number, since 2×57108721² = 6522812028511682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (57108781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 28554360 + 28554361.

It is an arithmetic number, because the mean of its divisors is an integer number (28554361).

Almost surely, 2^57108721 is an apocalyptic number.

It is an amenable number.

57108721 is a deficient number, since it is larger than the sum of its proper divisors (1).

57108721 is an equidigital number, since it uses as much as digits as its factorization.

57108721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3920, while the sum is 31.

The square root of 57108721 is about 7557.0312292593. The cubic root of 57108721 is about 385.0946436236.

Adding to 57108721 its reverse (12780175), we get a palindrome (69888896).

The spelling of 57108721 in words is "fifty-seven million, one hundred eight thousand, seven hundred twenty-one".