6401781 has 16 divisors (see below), whose sum is σ = 9717120. Its totient is φ = 4163040.

The previous prime is 6401771. The next prime is 6401827. The reversal of 6401781 is 1871046.

It is a happy number.

6401781 is a `hidden beast` number, since 640 + 17 + 8 + 1 = 666.

It is not a de Polignac number, because 6401781 - 2⁵ = 6401749 is a prime.

It is a super-2 number, since 2×6401781² = 81965599943922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6401761) 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, 1785 + ... + 3998.

It is an arithmetic number, because the mean of its divisors is an integer number (607320).

Almost surely, 2^6401781 is an apocalyptic number.

It is an amenable number.

6401781 is a deficient number, since it is larger than the sum of its proper divisors (3315339).

6401781 is a wasteful number, since it uses less digits than its factorization.

6401781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5833 (or 5827 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 6401781 is about 2530.1741046813. The cubic root of 6401781 is about 185.6807739758.

The spelling of 6401781 in words is "six million, four hundred one thousand, seven hundred eighty-one".