61721555 has 16 divisors (see below), whose sum is σ = 86617344. Its totient is φ = 41338080.

The previous prime is 61721549. The next prime is 61721563. The reversal of 61721555 is 55512716.

It is not a de Polignac number, because 61721555 - 2¹² = 61717459 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19001 + ... + 22010.

It is an arithmetic number, because the mean of its divisors is an integer number (5413584).

Almost surely, 2^61721555 is an apocalyptic number.

61721555 is a deficient number, since it is larger than the sum of its proper divisors (24895789).

61721555 is a wasteful number, since it uses less digits than its factorization.

61721555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41066.

The product of its digits is 10500, while the sum is 32.

The square root of 61721555 is about 7856.3067022616. The cubic root of 61721555 is about 395.1957690045.

The spelling of 61721555 in words is "sixty-one million, seven hundred twenty-one thousand, five hundred fifty-five".