2661221655 has 16 divisors (see below), whose sum is σ = 4731060960. Its totient is φ = 1419318144.

The previous prime is 2661221587. The next prime is 2661221659. The reversal of 2661221655 is 5561221662.

2661221655 is a `hidden beast` number, since 26 + 612 + 2 + 16 + 5 + 5 = 666.

It is not a de Polignac number, because 2661221655 - 2¹³ = 2661213463 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2661221659) by changing a digit.

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, 9856242 + ... + 9856511.

It is an arithmetic number, because the mean of its divisors is an integer number (295691310).

Almost surely, 2^2661221655 is an apocalyptic number.

2661221655 is a deficient number, since it is larger than the sum of its proper divisors (2069839305).

2661221655 is a wasteful number, since it uses less digits than its factorization.

2661221655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19712767 (or 19712761 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 2661221655 is about 51587.0299106277. The cubic root of 2661221655 is about 1385.7780655120.

The spelling of 2661221655 in words is "two billion, six hundred sixty-one million, two hundred twenty-one thousand, six hundred fifty-five".