400249981 has 2 divisors, whose sum is σ = 400249982. Its totient is φ = 400249980.

The previous prime is 400249973. The next prime is 400250009. The reversal of 400249981 is 189942004.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 338376025 + 61873956 = 18395^2 + 7866^2 .

It is a cyclic number.

It is not a de Polignac number, because 400249981 - 2³ = 400249973 is a prime.

It is a super-2 number, since 2×400249981² = 320400094581000722, which contains 22 as substring.

It is equal to p_21348928 and since 400249981 and 21348928 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 400249981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (400249951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200124990 + 200124991.

It is an arithmetic number, because the mean of its divisors is an integer number (200124991).

Almost surely, 2^400249981 is an apocalyptic number.

It is an amenable number.

400249981 is a deficient number, since it is larger than the sum of its proper divisors (1).

400249981 is an equidigital number, since it uses as much as digits as its factorization.

400249981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 400249981 is about 20006.2485488909. The cubic root of 400249981 is about 736.9597574109.

It can be divided in two parts, 40024 and 9981, that added together give a palindrome (50005).

The spelling of 400249981 in words is "four hundred million, two hundred forty-nine thousand, nine hundred eighty-one".