4000081 has 2 divisors, whose sum is σ = 4000082. Its totient is φ = 4000080.

The previous prime is 4000079. The next prime is 4000093. The reversal of 4000081 is 1800004.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4000000 + 81 = 2000^2 + 9^2 .

It is a cyclic number.

It is not a de Polignac number, because 4000081 - 2¹ = 4000079 is a prime.

It is a super-2 number, since 2×4000081² = 32001296013122, which contains 22 as substring.

Together with 4000079, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (4004081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2000040 + 2000041.

It is an arithmetic number, because the mean of its divisors is an integer number (2000041).

Almost surely, 2^4000081 is an apocalyptic number.

It is an amenable number.

4000081 is a deficient number, since it is larger than the sum of its proper divisors (1).

4000081 is an equidigital number, since it uses as much as digits as its factorization.

4000081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 4000081 is about 2000.0202498975. The cubic root of 4000081 is about 158.7411766853.

Adding to 4000081 its reverse (1800004), we get a palindrome (5800085).

It can be divided in two parts, 40000 and 81, that multiplied together give a square (3240000 = 1800²).

The spelling of 4000081 in words is "four million, eighty-one", and thus it is an aban number.