216561621689 has 4 divisors (see below), whose sum is σ = 247498996224. Its totient is φ = 185624247156.

The previous prime is 216561621667. The next prime is 216561621701. The reversal of 216561621689 is 986126165612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216561621689 - 2¹⁶ = 216561556153 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 216561621689.

It is not an unprimeable number, because it can be changed into a prime (216561621629) 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 3 ways as a sum of consecutive naturals, for example, 15468687257 + ... + 15468687270.

It is an arithmetic number, because the mean of its divisors is an integer number (61874749056).

Almost surely, 2^216561621689 is an apocalyptic number.

It is an amenable number.

216561621689 is a deficient number, since it is larger than the sum of its proper divisors (30937374535).

216561621689 is an equidigital number, since it uses as much as digits as its factorization.

216561621689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30937374534.

The product of its digits is 1866240, while the sum is 53.

The spelling of 216561621689 in words is "two hundred sixteen billion, five hundred sixty-one million, six hundred twenty-one thousand, six hundred eighty-nine".