6405561 has 20 divisors (see below), whose sum is σ = 9881344. Its totient is φ = 4131000.

The previous prime is 6405559. The next prime is 6405577. The reversal of 6405561 is 1655046.

It is a happy number.

It is not a de Polignac number, because 6405561 - 2¹ = 6405559 is a prime.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6405541) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1236 + ... + 3786.

Almost surely, 2^6405561 is an apocalyptic number.

It is an amenable number.

6405561 is a deficient number, since it is larger than the sum of its proper divisors (3475783).

6405561 is a wasteful number, since it uses less digits than its factorization.

6405561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2594 (or 2585 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 6405561 is about 2530.9209786163. The cubic root of 6405561 is about 185.7173125176.

The spelling of 6405561 in words is "six million, four hundred five thousand, five hundred sixty-one".