8211561681 has 8 divisors (see below), whose sum is σ = 10951541440. Its totient is φ = 5472978192.

The previous prime is 8211561661. The next prime is 8211561703. The reversal of 8211561681 is 1861651128.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 8211561681 - 2²⁵ = 8178007249 is a prime.

It is a super-2 number, since 2×8211561681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8211561661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 335266 + ... + 358923.

It is an arithmetic number, because the mean of its divisors is an integer number (1368942680).

Almost surely, 2^8211561681 is an apocalyptic number.

It is an amenable number.

8211561681 is a deficient number, since it is larger than the sum of its proper divisors (2739979759).

8211561681 is a wasteful number, since it uses less digits than its factorization.

8211561681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 698135.

The product of its digits is 23040, while the sum is 39.

The square root of 8211561681 is about 90617.6675985428. The cubic root of 8211561681 is about 2017.4769729379.

The spelling of 8211561681 in words is "eight billion, two hundred eleven million, five hundred sixty-one thousand, six hundred eighty-one".