2181156532661 has 16 divisors (see below), whose sum is σ = 2294754325248. Its totient is φ = 2070800121600.

The previous prime is 2181156532601. The next prime is 2181156532729. The reversal of 2181156532661 is 1662356511812.

It is a cyclic number.

It is not a de Polignac number, because 2181156532661 - 2²⁶ = 2181089423797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181156532601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1804856 + ... + 2760401.

It is an arithmetic number, because the mean of its divisors is an integer number (143422145328).

Almost surely, 2^{2181156532661} is an apocalyptic number.

It is an amenable number.

2181156532661 is a deficient number, since it is larger than the sum of its proper divisors (113597792587).

2181156532661 is a wasteful number, since it uses less digits than its factorization.

2181156532661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4565612.

The product of its digits is 518400, while the sum is 47.

The spelling of 2181156532661 in words is "two trillion, one hundred eighty-one billion, one hundred fifty-six million, five hundred thirty-two thousand, six hundred sixty-one".