400243981 has 2 divisors, whose sum is σ = 400243982. Its totient is φ = 400243980.

The previous prime is 400243973. The next prime is 400244021. The reversal of 400243981 is 189342004.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 302412100 + 97831881 = 17390^2 + 9891^2 .

It is a cyclic number.

It is not a de Polignac number, because 400243981 - 2³ = 400243973 is a prime.

It is a super-2 number, since 2×400243981² = 320390488653456722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (400243951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200121990 + 200121991.

It is an arithmetic number, because the mean of its divisors is an integer number (200121991).

Almost surely, 2^400243981 is an apocalyptic number.

It is an amenable number.

400243981 is a deficient number, since it is larger than the sum of its proper divisors (1).

400243981 is an equidigital number, since it uses as much as digits as its factorization.

400243981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6912, while the sum is 31.

The square root of 400243981 is about 20006.0985951784. The cubic root of 400243981 is about 736.9560748951.

Adding to 400243981 its reverse (189342004), we get a palindrome (589585985).

The spelling of 400243981 in words is "four hundred million, two hundred forty-three thousand, nine hundred eighty-one".