2661561243 has 12 divisors (see below), whose sum is σ = 4193975448. Its totient is φ = 1613067360.

The previous prime is 2661561241. The next prime is 2661561247. The reversal of 2661561243 is 3421651662.

2661561243 is a `hidden beast` number, since 26 + 6 + 15 + 612 + 4 + 3 = 666.

It is not a de Polignac number, because 2661561243 - 2¹ = 2661561241 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 2661561198 and 2661561207.

It is not an unprimeable number, because it can be changed into a prime (2661561241) 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 11 ways as a sum of consecutive naturals, for example, 13442130 + ... + 13442327.

It is an arithmetic number, because the mean of its divisors is an integer number (349497954).

Almost surely, 2^2661561243 is an apocalyptic number.

2661561243 is a deficient number, since it is larger than the sum of its proper divisors (1532414205).

2661561243 is a wasteful number, since it uses less digits than its factorization.

2661561243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26884474 (or 26884471 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 2661561243 is about 51590.3212143518. The cubic root of 2661561243 is about 1385.8370075629.

The spelling of 2661561243 in words is "two billion, six hundred sixty-one million, five hundred sixty-one thousand, two hundred forty-three".