218088758481661 has 4 divisors (see below), whose sum is σ = 225609060498300. Its totient is φ = 210568456465024.

The previous prime is 218088758481653. The next prime is 218088758481677. The reversal of 218088758481661 is 166184857880812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 60098062262436 + 157990696219225 = 7752294^2 + 12569435^2 .

It is a cyclic number.

It is not a de Polignac number, because 218088758481661 - 2³ = 218088758481653 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 (218088758481761) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3760151008276 + ... + 3760151008333.

It is an arithmetic number, because the mean of its divisors is an integer number (56402265124575).

Almost surely, 2^{218088758481661} is an apocalyptic number.

It is an amenable number.

218088758481661 is a deficient number, since it is larger than the sum of its proper divisors (7520302016639).

218088758481661 is an equidigital number, since it uses as much as digits as its factorization.

218088758481661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7520302016638.

The product of its (nonzero) digits is 330301440, while the sum is 73.

The spelling of 218088758481661 in words is "two hundred eighteen trillion, eighty-eight billion, seven hundred fifty-eight million, four hundred eighty-one thousand, six hundred sixty-one".