6561651 has 4 divisors (see below), whose sum is σ = 8748872. Its totient is φ = 4374432.

The previous prime is 6561649. The next prime is 6561673. The reversal of 6561651 is 1561656.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 6561651 - 2¹ = 6561649 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6561151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1093606 + ... + 1093611.

It is an arithmetic number, because the mean of its divisors is an integer number (2187218).

Almost surely, 2^6561651 is an apocalyptic number.

6561651 is a deficient number, since it is larger than the sum of its proper divisors (2187221).

6561651 is a wasteful number, since it uses less digits than its factorization.

6561651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2187220.

The product of its digits is 5400, while the sum is 30.

The square root of 6561651 is about 2561.5719782977. The cubic root of 6561651 is about 187.2137356146.

It can be divided in two parts, 65 and 61651, that added together give a palindrome (61716).

The spelling of 6561651 in words is "six million, five hundred sixty-one thousand, six hundred fifty-one".