400781 has 4 divisors (see below), whose sum is σ = 403200. Its totient is φ = 398364.

The previous prime is 400759. The next prime is 400823. The reversal of 400781 is 187004.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 400781 - 2¹⁰ = 399757 is a prime.

It is a super-2 number, since 2×400781² = 321250819922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400711) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 941 + ... + 1298.

It is an arithmetic number, because the mean of its divisors is an integer number (100800).

2⁴⁰⁰⁷⁸¹ is an apocalyptic number.

It is an amenable number.

400781 is a deficient number, since it is larger than the sum of its proper divisors (2419).

400781 is a wasteful number, since it uses less digits than its factorization.

400781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2418.

The product of its (nonzero) digits is 224, while the sum is 20.

The square root of 400781 is about 633.0726656554. The cubic root of 400781 is about 73.7285526067.

Adding to 400781 its reverse (187004), we get a palindrome (587785).

The spelling of 400781 in words is "four hundred thousand, seven hundred eighty-one".