1221642661545 has 12 divisors (see below), whose sum is σ = 2117513946756. Its totient is φ = 651542752800.

The previous prime is 1221642661543. The next prime is 1221642661573. The reversal of 1221642661545 is 5451662461221.

1221642661545 is a `hidden beast` number, since 1 + 2 + 2 + 1 + 6 + 4 + 26 + 615 + 4 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 161276134464 + 1060366527081 = 401592^2 + 1029741^2 .

It is not a de Polignac number, because 1221642661545 - 2¹ = 1221642661543 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 27147614701 = 1221642661545 / (1 + 2 + 2 + 1 + 6 + 4 + 2 + 6 + 6 + 1 + 5 + 4 + 5).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1221642661545.

It is not an unprimeable number, because it can be changed into a prime (1221642661541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13573807306 + ... + 13573807395.

It is an arithmetic number, because the mean of its divisors is an integer number (176459495563).

Almost surely, 2^{1221642661545} is an apocalyptic number.

1221642661545 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1221642661545 is a deficient number, since it is larger than the sum of its proper divisors (895871285211).

1221642661545 is a wasteful number, since it uses less digits than its factorization.

1221642661545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27147614712 (or 27147614709 counting only the distinct ones).

The product of its digits is 691200, while the sum is 45.

The spelling of 1221642661545 in words is "one trillion, two hundred twenty-one billion, six hundred forty-two million, six hundred sixty-one thousand, five hundred forty-five".