400028781 has 16 divisors (see below), whose sum is σ = 541291968. Its totient is φ = 262752000.

The previous prime is 400028777. The next prime is 400028803. The reversal of 400028781 is 187820004.

It is not a de Polignac number, because 400028781 - 2² = 400028777 is a prime.

It is a super-2 number, since 2×400028781² = 320046051256691922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400028731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 60805 + ... + 67061.

It is an arithmetic number, because the mean of its divisors is an integer number (33830748).

Almost surely, 2^400028781 is an apocalyptic number.

It is an amenable number.

400028781 is a deficient number, since it is larger than the sum of its proper divisors (141263187).

400028781 is a wasteful number, since it uses less digits than its factorization.

400028781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6572.

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 400028781 is about 20000.7195120576. The cubic root of 400028781 is about 736.8239709893.

Adding to 400028781 its reverse (187820004), we get a palindrome (587848785).

The spelling of 400028781 in words is "four hundred million, twenty-eight thousand, seven hundred eighty-one".