4000399981 has 2 divisors, whose sum is σ = 4000399982. Its totient is φ = 4000399980.

The previous prime is 4000399969. The next prime is 4000400023. The reversal of 4000399981 is 1899930004.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2455202500 + 1545197481 = 49550^2 + 39309^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-4000399981 is a prime.

It is a super-2 number, since 2×4000399981² = 32006400015969600722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (4000369981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2000199990 + 2000199991.

It is an arithmetic number, because the mean of its divisors is an integer number (2000199991).

Almost surely, 2^4000399981 is an apocalyptic number.

It is an amenable number.

4000399981 is a deficient number, since it is larger than the sum of its proper divisors (1).

4000399981 is an equidigital number, since it uses as much as digits as its factorization.

4000399981 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 4000399981 is about 63248.7152517741. The cubic root of 4000399981 is about 1587.4539610597.

The spelling of 4000399981 in words is "four billion, three hundred ninety-nine thousand, nine hundred eighty-one".