81945331 has 4 divisors (see below), whose sum is σ = 88248832. Its totient is φ = 75641832.

The previous prime is 81945323. The next prime is 81945337. The reversal of 81945331 is 13354918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13354918 = 2 ⋅6677459.

It is a cyclic number.

It is not a de Polignac number, because 81945331 - 2³ = 81945323 is a prime.

It is a super-2 number, since 2×81945331² = 13430074545399122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81945337) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3151731 + ... + 3151756.

It is an arithmetic number, because the mean of its divisors is an integer number (22062208).

Almost surely, 2^81945331 is an apocalyptic number.

81945331 is a deficient number, since it is larger than the sum of its proper divisors (6303501).

81945331 is a wasteful number, since it uses less digits than its factorization.

81945331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6303500.

The product of its digits is 12960, while the sum is 34.

The square root of 81945331 is about 9052.3660443002. The cubic root of 81945331 is about 434.3515789591.

The spelling of 81945331 in words is "eighty-one million, nine hundred forty-five thousand, three hundred thirty-one".