3651581 has 6 divisors (see below), whose sum is σ = 3701082. Its totient is φ = 3602720.

The previous prime is 3651559. The next prime is 3651607. The reversal of 3651581 is 1851563.

It can be written as a sum of positive squares in 3 ways, for example, as 3481 + 3648100 = 59^2 + 1910^2 .

It is not a de Polignac number, because 3651581 - 2¹⁴ = 3635197 is a prime.

It is a super-4 number, since 4×3651581⁴ (a number of 27 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3651281) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 7691 + ... + 8151.

It is an arithmetic number, because the mean of its divisors is an integer number (616847).

Almost surely, 2^3651581 is an apocalyptic number.

It is an amenable number.

3651581 is a deficient number, since it is larger than the sum of its proper divisors (49501).

3651581 is an frugal number, since it uses more digits than its factorization.

3651581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 639 (or 550 counting only the distinct ones).

The product of its digits is 3600, while the sum is 29.

The square root of 3651581 is about 1910.9110392690. The cubic root of 3651581 is about 153.9903996939.

The spelling of 3651581 in words is "three million, six hundred fifty-one thousand, five hundred eighty-one".