56172821 has 2 divisors, whose sum is σ = 56172822. Its totient is φ = 56172820.

The previous prime is 56172799. The next prime is 56172827. The reversal of 56172821 is 12827165.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37075921 + 19096900 = 6089^2 + 4370^2 .

It is a cyclic number.

It is not a de Polignac number, because 56172821 - 2⁶ = 56172757 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (56172827) 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 as a sum of consecutive naturals, namely, 28086410 + 28086411.

It is an arithmetic number, because the mean of its divisors is an integer number (28086411).

Almost surely, 2^56172821 is an apocalyptic number.

It is an amenable number.

56172821 is a deficient number, since it is larger than the sum of its proper divisors (1).

56172821 is an equidigital number, since it uses as much as digits as its factorization.

56172821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6720, while the sum is 32.

The square root of 56172821 is about 7494.8529672036. The cubic root of 56172821 is about 382.9793974833.

Adding to 56172821 its reverse (12827165), we get a palindrome (68999986).

The spelling of 56172821 in words is "fifty-six million, one hundred seventy-two thousand, eight hundred twenty-one".