55731721 has 2 divisors, whose sum is σ = 55731722. Its totient is φ = 55731720.

The previous prime is 55731719. The next prime is 55731733. The reversal of 55731721 is 12713755.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 52707600 + 3024121 = 7260^2 + 1739^2 .

It is a cyclic number.

It is not a de Polignac number, because 55731721 - 2¹ = 55731719 is a prime.

Together with 55731719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (55731701) 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, 27865860 + 27865861.

It is an arithmetic number, because the mean of its divisors is an integer number (27865861).

Almost surely, 2^55731721 is an apocalyptic number.

It is an amenable number.

55731721 is a deficient number, since it is larger than the sum of its proper divisors (1).

55731721 is an equidigital number, since it uses as much as digits as its factorization.

55731721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7350, while the sum is 31.

The square root of 55731721 is about 7465.3681088075. The cubic root of 55731721 is about 381.9743068161.

The spelling of 55731721 in words is "fifty-five million, seven hundred thirty-one thousand, seven hundred twenty-one".