1091671818561 has 27 divisors (see below), whose sum is σ = 1604310491329. Its totient is φ = 715324737192.

The previous prime is 1091671818547. The next prime is 1091671818617. The reversal of 1091671818561 is 1658181761901.

The square root of 1091671818561 is 1044831.

It is a perfect power (a square), and thus also a powerful number.

1091671818561 is a `hidden beast` number, since 1 + 0 + 9 + 1 + 6 + 71 + 8 + 1 + 8 + 561 = 666.

It is not a de Polignac number, because 1091671818561 - 2³⁵ = 1057312080193 is a prime.

It is a super-2 number, since 2×1091671818561² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1091671818498 and 1091671818507.

It is not an unprimeable number, because it can be changed into a prime (1091671818511) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 184932136 + ... + 184938038.

Almost surely, 2^{1091671818561} is an apocalyptic number.

1091671818561 is the 1044831-st square number.

1091671818561 is the 522416-th centered octagonal number.

It is an amenable number.

1091671818561 is a deficient number, since it is larger than the sum of its proper divisors (512638672768).

1091671818561 is an frugal number, since it uses more digits than its factorization.

1091671818561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11930 (or 5965 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 54.

The spelling of 1091671818561 in words is "one trillion, ninety-one billion, six hundred seventy-one million, eight hundred eighteen thousand, five hundred sixty-one".