55540721 has 2 divisors, whose sum is σ = 55540722. Its totient is φ = 55540720.

The previous prime is 55540703. The next prime is 55540733. The reversal of 55540721 is 12704555.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 49900096 + 5640625 = 7064^2 + 2375^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-55540721 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (55540741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 27770360 + 27770361.

It is an arithmetic number, because the mean of its divisors is an integer number (27770361).

Almost surely, 2^55540721 is an apocalyptic number.

It is an amenable number.

55540721 is a deficient number, since it is larger than the sum of its proper divisors (1).

55540721 is an equidigital number, since it uses as much as digits as its factorization.

55540721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7000, while the sum is 29.

The square root of 55540721 is about 7452.5647263207. The cubic root of 55540721 is about 381.5374485070.

The spelling of 55540721 in words is "fifty-five million, five hundred forty thousand, seven hundred twenty-one".