56505721 has 2 divisors, whose sum is σ = 56505722. Its totient is φ = 56505720.

The previous prime is 56505719. The next prime is 56505731. The reversal of 56505721 is 12750565.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 39200121 + 17305600 = 6261^2 + 4160^2 .

It is a cyclic number.

It is not a de Polignac number, because 56505721 - 2¹ = 56505719 is a prime.

Together with 56505719, it forms a pair of twin primes.

It is equal to p_3366643 and since 56505721 and 3366643 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (56505731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 28252860 + 28252861.

It is an arithmetic number, because the mean of its divisors is an integer number (28252861).

Almost surely, 2^56505721 is an apocalyptic number.

It is an amenable number.

56505721 is a deficient number, since it is larger than the sum of its proper divisors (1).

56505721 is an equidigital number, since it uses as much as digits as its factorization.

56505721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10500, while the sum is 31.

The square root of 56505721 is about 7517.0287348127. The cubic root of 56505721 is about 383.7344649534.

The spelling of 56505721 in words is "fifty-six million, five hundred five thousand, seven hundred twenty-one".