55042721 has 2 divisors, whose sum is σ = 55042722. Its totient is φ = 55042720.

The previous prime is 55042661. The next prime is 55042723. The reversal of 55042721 is 12724055.

55042721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 48094225 + 6948496 = 6935^2 + 2636^2 .

It is a cyclic number.

It is not a de Polignac number, because 55042721 - 2¹⁸ = 54780577 is a prime.

It is a super-2 number, since 2×55042721² = 6059402270167682, which contains 22 as substring.

Together with 55042723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (55042723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 27521360 + 27521361.

It is an arithmetic number, because the mean of its divisors is an integer number (27521361).

Almost surely, 2^55042721 is an apocalyptic number.

It is an amenable number.

55042721 is a deficient number, since it is larger than the sum of its proper divisors (1).

55042721 is an equidigital number, since it uses as much as digits as its factorization.

55042721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 55042721 is about 7419.0781772401. The cubic root of 55042721 is about 380.3936847945.

Adding to 55042721 its reverse (12724055), we get a palindrome (67766776).

The spelling of 55042721 in words is "fifty-five million, forty-two thousand, seven hundred twenty-one".