8921516661 has 20 divisors (see below), whose sum is σ = 13509777292. Its totient is φ = 5866198848.

The previous prime is 8921516657. The next prime is 8921516707. The reversal of 8921516661 is 1666151298.

It can be written as a sum of positive squares in 2 ways, for example, as 7105478436 + 1816038225 = 84294^2 + 42615^2 .

It is not a de Polignac number, because 8921516661 - 2² = 8921516657 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 (8921511661) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 748486 + ... + 760311.

Almost surely, 2^8921516661 is an apocalyptic number.

8921516661 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

8921516661 is a deficient number, since it is larger than the sum of its proper divisors (4588260631).

8921516661 is a wasteful number, since it uses less digits than its factorization.

8921516661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1508882 (or 1508873 counting only the distinct ones).

The product of its digits is 155520, while the sum is 45.

The square root of 8921516661 is about 94453.7805543007. The cubic root of 8921516661 is about 2074.0197943343.

The spelling of 8921516661 in words is "eight billion, nine hundred twenty-one million, five hundred sixteen thousand, six hundred sixty-one".