8661981 has 8 divisors (see below), whose sum is σ = 11947680. Its totient is φ = 5575472.

The previous prime is 8661977. The next prime is 8661997. The reversal of 8661981 is 1891668.

8661981 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 8661981 - 2² = 8661977 is a prime.

It is a super-2 number, since 2×8661981² = 150059829688722, which contains 22 as substring.

It is a Curzon number.

8661981 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8661901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49695 + ... + 49868.

It is an arithmetic number, because the mean of its divisors is an integer number (1493460).

Almost surely, 2^8661981 is an apocalyptic number.

It is an amenable number.

8661981 is a deficient number, since it is larger than the sum of its proper divisors (3285699).

8661981 is a wasteful number, since it uses less digits than its factorization.

8661981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99595.

The product of its digits is 20736, while the sum is 39.

The square root of 8661981 is about 2943.1243602675. The cubic root of 8661981 is about 205.3709800423.

The spelling of 8661981 in words is "eight million, six hundred sixty-one thousand, nine hundred eighty-one".