6521661 has 8 divisors (see below), whose sum is σ = 9661760. Its totient is φ = 4347756.

The previous prime is 6521587. The next prime is 6521677. The reversal of 6521661 is 1661256.

It is a happy number.

6521661 is a `hidden beast` number, since 652 + 1 + 6 + 6 + 1 = 666.

It is not a de Polignac number, because 6521661 - 2⁷ = 6521533 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 241543 = 6521661 / (6 + 5 + 2 + 1 + 6 + 6 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6521561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 120745 + ... + 120798.

It is an arithmetic number, because the mean of its divisors is an integer number (1207720).

Almost surely, 2^6521661 is an apocalyptic number.

It is an amenable number.

6521661 is a deficient number, since it is larger than the sum of its proper divisors (3140099).

6521661 is a wasteful number, since it uses less digits than its factorization.

6521661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241552 (or 241546 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 6521661 is about 2553.7542951506. The cubic root of 6521661 is about 186.8326354827.

The spelling of 6521661 in words is "six million, five hundred twenty-one thousand, six hundred sixty-one".