4001781 has 16 divisors (see below), whose sum is σ = 6224000. Its totient is φ = 2286144.

The previous prime is 4001779. The next prime is 4001791. The reversal of 4001781 is 1871004.

It is not a de Polignac number, because 4001781 - 2¹ = 4001779 is a prime.

It is a super-2 number, since 2×4001781² = 32028502343922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4001741) 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, 916 + ... + 2973.

It is an arithmetic number, because the mean of its divisors is an integer number (389000).

Almost surely, 2^4001781 is an apocalyptic number.

It is an amenable number.

4001781 is a deficient number, since it is larger than the sum of its proper divisors (2222219).

4001781 is an equidigital number, since it uses as much as digits as its factorization.

4001781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3913 (or 3899 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 21.

The square root of 4001781 is about 2000.4452004491. The cubic root of 4001781 is about 158.7636613783.

Adding to 4001781 its reverse (1871004), we get a palindrome (5872785).

The spelling of 4001781 in words is "four million, one thousand, seven hundred eighty-one".