400128731 has 2 divisors, whose sum is σ = 400128732. Its totient is φ = 400128730.

The previous prime is 400128727. The next prime is 400128793. The reversal of 400128731 is 137821004.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 400128731 - 2² = 400128727 is a prime.

It is a super-2 number, since 2×400128731² = 320206002743340722, which contains 22 as substring.

It is a Chen prime.

It is equal to p_21342752 and since 400128731 and 21342752 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 400128731.

It is not a weakly prime, because it can be changed into another prime (400128721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200064365 + 200064366.

It is an arithmetic number, because the mean of its divisors is an integer number (200064366).

Almost surely, 2^400128731 is an apocalyptic number.

400128731 is a deficient number, since it is larger than the sum of its proper divisors (1).

400128731 is an equidigital number, since it uses as much as digits as its factorization.

400128731 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 400128731 is about 20003.2180161093. The cubic root of 400128731 is about 736.8853327602.

Adding to 400128731 its reverse (137821004), we get a palindrome (537949735).

The spelling of 400128731 in words is "four hundred million, one hundred twenty-eight thousand, seven hundred thirty-one".