81109981 has 8 divisors (see below), whose sum is σ = 85307904. Its totient is φ = 77010960.

The previous prime is 81109939. The next prime is 81110023. The reversal of 81109981 is 18990118.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81109939) and next prime (81110023).

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 81109981 - 2¹³ = 81101789 is a prime.

It is a super-2 number, since 2×81109981² = 13157658035640722, which contains 22 as substring.

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 81109981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81109681) 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, 23041 + ... + 26326.

It is an arithmetic number, because the mean of its divisors is an integer number (10663488).

Almost surely, 2^81109981 is an apocalyptic number.

It is an amenable number.

81109981 is a deficient number, since it is larger than the sum of its proper divisors (4197923).

81109981 is a wasteful number, since it uses less digits than its factorization.

81109981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49451.

The product of its (nonzero) digits is 5184, while the sum is 37.

The square root of 81109981 is about 9006.1079829191. The cubic root of 81109981 is about 432.8706097505.

The spelling of 81109981 in words is "eighty-one million, one hundred nine thousand, nine hundred eighty-one".