8131981 has 32 divisors (see below), whose sum is σ = 10442880. Its totient is φ = 6220800.

The previous prime is 8131969. The next prime is 8131993. The reversal of 8131981 is 1891318.

8131981 = T₁₂₃ + T₁₂₄ + ... + T₃₆₉.

It is an interprime number because it is at equal distance from previous prime (8131969) and next prime (8131993).

It is a 5-Lehmer number, since φ(8131981) divides (8131981-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 8131981 - 2⁷ = 8131853 is a prime.

It is a super-2 number, since 2×8131981² = 132258229968722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

8131981 is a lucky number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8131901) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 111361 + ... + 111433.

It is an arithmetic number, because the mean of its divisors is an integer number (326340).

Almost surely, 2^8131981 is an apocalyptic number.

It is an amenable number.

8131981 is a deficient number, since it is larger than the sum of its proper divisors (2310899).

8131981 is a wasteful number, since it uses less digits than its factorization.

8131981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157.

The product of its digits is 1728, while the sum is 31.

The square root of 8131981 is about 2851.6628482343. The cubic root of 8131981 is about 201.0938482402.

The spelling of 8131981 in words is "eight million, one hundred thirty-one thousand, nine hundred eighty-one".