3645991 has 4 divisors (see below), whose sum is σ = 3650584. Its totient is φ = 3641400.

The previous prime is 3645979. The next prime is 3645997. The reversal of 3645991 is 1995463.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1995463 = 109 ⋅18307.

It is a cyclic number.

It is not a de Polignac number, because 3645991 - 2⁵ = 3645959 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 3645991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3645997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 765 + ... + 2806.

It is an arithmetic number, because the mean of its divisors is an integer number (912646).

Almost surely, 2^3645991 is an apocalyptic number.

3645991 is the 1021-st nonagonal number.

3645991 is a deficient number, since it is larger than the sum of its proper divisors (4593).

3645991 is a wasteful number, since it uses less digits than its factorization.

3645991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4592.

The product of its digits is 29160, while the sum is 37.

The square root of 3645991 is about 1909.4478259434. The cubic root of 3645991 is about 153.9117811483.

The spelling of 3645991 in words is "three million, six hundred forty-five thousand, nine hundred ninety-one".