3551661 has 8 divisors (see below), whose sum is σ = 5261760. Its totient is φ = 2367756.

The previous prime is 3551641. The next prime is 3551663. The reversal of 3551661 is 1661553.

It is a happy number.

It is not a de Polignac number, because 3551661 - 2⁵ = 3551629 is a prime.

It is a super-2 number, since 2×3551661² = 25228591717842, which contains 22 as substring.

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: 131543 = 3551661 / (3 + 5 + 5 + 1 + 6 + 6 + 1).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3551663) 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, 65745 + ... + 65798.

It is an arithmetic number, because the mean of its divisors is an integer number (657720).

Almost surely, 2^3551661 is an apocalyptic number.

It is an amenable number.

3551661 is a deficient number, since it is larger than the sum of its proper divisors (1710099).

3551661 is a wasteful number, since it uses less digits than its factorization.

3551661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131552 (or 131546 counting only the distinct ones).

The product of its digits is 2700, while the sum is 27.

The square root of 3551661 is about 1884.5851002276. The cubic root of 3551661 is about 152.5728183995.

It can be divided in two parts, 355 and 1661, that added together give a triangular number (2016 = T₆₃).

The spelling of 3551661 in words is "three million, five hundred fifty-one thousand, six hundred sixty-one".