40399981 has 2 divisors, whose sum is σ = 40399982. Its totient is φ = 40399980.

The previous prime is 40399979. The next prime is 40400011. The reversal of 40399981 is 18999304.

40399981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 37393225 + 3006756 = 6115^2 + 1734^2 .

It is a cyclic number.

It is not a de Polignac number, because 40399981 - 2¹ = 40399979 is a prime.

It is a super-2 number, since 2×40399981² = 3264316929600722, which contains 22 as substring.

Together with 40399979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (40399901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20199990 + 20199991.

It is an arithmetic number, because the mean of its divisors is an integer number (20199991).

Almost surely, 2^40399981 is an apocalyptic number.

It is an amenable number.

40399981 is a deficient number, since it is larger than the sum of its proper divisors (1).

40399981 is an equidigital number, since it uses as much as digits as its factorization.

40399981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69984, while the sum is 43.

The square root of 40399981 is about 6356.0979382008. The cubic root of 40399981 is about 343.1313405331.

The spelling of 40399981 in words is "forty million, three hundred ninety-nine thousand, nine hundred eighty-one".