56691721 has 2 divisors, whose sum is σ = 56691722. Its totient is φ = 56691720.

The previous prime is 56691709. The next prime is 56691731. The reversal of 56691721 is 12719665.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 55950400 + 741321 = 7480^2 + 861^2 .

It is a cyclic number.

It is not a de Polignac number, because 56691721 - 2⁵ = 56691689 is a prime.

It is not a weakly prime, because it can be changed into another prime (56691731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 28345860 + 28345861.

It is an arithmetic number, because the mean of its divisors is an integer number (28345861).

Almost surely, 2^56691721 is an apocalyptic number.

It is an amenable number.

56691721 is a deficient number, since it is larger than the sum of its proper divisors (1).

56691721 is an equidigital number, since it uses as much as digits as its factorization.

56691721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 37.

The square root of 56691721 is about 7529.3904799791. The cubic root of 56691721 is about 384.1550503235.

The spelling of 56691721 in words is "fifty-six million, six hundred ninety-one thousand, seven hundred twenty-one".